diff --git a/Sources/SwiftDoc/API.swift b/Sources/SwiftDoc/API.swift
index dbdb7af2..aaa6cb0b 100644
--- a/Sources/SwiftDoc/API.swift
+++ b/Sources/SwiftDoc/API.swift
@@ -55,3 +55,9 @@ extension Subscript: API {
 
 extension Typealias: API {}
 extension Variable: API {}
+
+public enum AccessLevel: String, Codable {
+    case `public`
+    case `internal`
+    case `private`
+}
diff --git a/Sources/SwiftDoc/Interface.swift b/Sources/SwiftDoc/Interface.swift
index 9370790d..774b05b6 100644
--- a/Sources/SwiftDoc/Interface.swift
+++ b/Sources/SwiftDoc/Interface.swift
@@ -5,10 +5,12 @@ import struct SwiftSemantics.Protocol
 public final class Interface: Codable {
     public let imports: [Import]
     public let symbols: [Symbol]
+    public let minimumAccessLevel: AccessLevel
 
-    public required init(imports: [Import], symbols: [Symbol]) {
+    public required init(imports: [Import], symbols: [Symbol], minimumAccessLevel: AccessLevel) {
         self.imports = imports
-        self.symbols = symbols.filter { $0.isPublic }
+        self.symbols = symbols.filter { $0.isIncluded(minimumAccessLevel: minimumAccessLevel) }
+        self.minimumAccessLevel = minimumAccessLevel
     }
 
     // MARK: -
@@ -37,7 +39,7 @@ public final class Interface: Codable {
             var superclasses = Set(CollectionOfOne(baseClass))
 
             while !superclasses.isEmpty {
-                let subclasses = Set(superclasses.flatMap { typesInheriting(from: $0) }.filter { $0.isPublic })
+                let subclasses = Set(superclasses.flatMap { typesInheriting(from: $0) }.filter { $0.isIncluded(minimumAccessLevel: self.minimumAccessLevel) })
                 defer { superclasses = subclasses }
                 classClusters[baseClass, default: []].formUnion(subclasses)
             }
diff --git a/Sources/SwiftDoc/Module.swift b/Sources/SwiftDoc/Module.swift
index 009346ed..a43063ac 100644
--- a/Sources/SwiftDoc/Module.swift
+++ b/Sources/SwiftDoc/Module.swift
@@ -7,18 +7,21 @@ public final class Module: Codable {
 
     public let sourceFiles: [SourceFile]
 
+    public let minimumAccessLevel: AccessLevel
+    
     public lazy var interface: Interface = {
         let imports = sourceFiles.flatMap { $0.imports }
         let symbols = sourceFiles.flatMap { $0.symbols }
-        return Interface(imports: imports, symbols: symbols)
+        return Interface(imports: imports, symbols: symbols, minimumAccessLevel: minimumAccessLevel)
     }()
 
-    public required init(name: String = "Anonymous", sourceFiles: [SourceFile]) {
+    public required init(name: String = "Anonymous", sourceFiles: [SourceFile], minimumAccessLevel: AccessLevel) {
         self.name = name
         self.sourceFiles = sourceFiles
+        self.minimumAccessLevel = minimumAccessLevel
     }
 
-    public convenience init(name: String = "Anonymous", paths: [String]) throws {
+    public convenience init(name: String = "Anonymous", paths: [String], minimumAccessLevel: AccessLevel) throws {
         var sources: [(file: URL, directory: URL)] = []
 
         let fileManager = FileManager.default
@@ -38,6 +41,6 @@ public final class Module: Codable {
 
         let sourceFiles = try sources.parallelMap { try SourceFile(file: $0.file, relativeTo: $0.directory) }
 
-        self.init(name: name, sourceFiles: sourceFiles)
+        self.init(name: name, sourceFiles: sourceFiles, minimumAccessLevel: minimumAccessLevel)
     }
 }
diff --git a/Sources/SwiftDoc/Symbol.swift b/Sources/SwiftDoc/Symbol.swift
index c41f5933..c5ce8dca 100644
--- a/Sources/SwiftDoc/Symbol.swift
+++ b/Sources/SwiftDoc/Symbol.swift
@@ -58,7 +58,26 @@ public final class Symbol {
 
         return false
     }
-
+    
+    public var isInternal: Bool {
+        if api.modifiers.contains(where: { $0.name == "private" }) {
+            return false
+        }
+        
+        return true
+    }
+    
+    public func isIncluded(minimumAccessLevel: AccessLevel) -> Bool {
+        switch minimumAccessLevel {
+        case .public:
+            return isPublic
+        case .internal:
+            return isInternal
+        case .private:
+            return true
+        }
+    }
+    
     public var isDocumented: Bool {
         return documentation?.isEmpty == false
     }
diff --git a/Sources/swift-doc/Extensions/DCOV+Extensions.swift b/Sources/swift-doc/Extensions/DCOV+Extensions.swift
index fbd423cd..0fdf1f53 100644
--- a/Sources/swift-doc/Extensions/DCOV+Extensions.swift
+++ b/Sources/swift-doc/Extensions/DCOV+Extensions.swift
@@ -21,7 +21,7 @@ extension Report {
     public init(module: Module) {
         let entries = module.sourceFiles
                             .flatMap { $0.symbols }
-                            .filter { $0.isPublic }
+                            .filter { $0.isIncluded(minimumAccessLevel: module.minimumAccessLevel) }
                             .map { Entry($0) }
 
         self.init(entries: entries)
diff --git a/Sources/swift-doc/Subcommands/Coverage.swift b/Sources/swift-doc/Subcommands/Coverage.swift
index 4fbf4d7c..08312794 100644
--- a/Sources/swift-doc/Subcommands/Coverage.swift
+++ b/Sources/swift-doc/Subcommands/Coverage.swift
@@ -9,6 +9,11 @@ extension SwiftDoc {
             @Argument(help: "One or more paths to Swift files")
             var inputs: [String]
 
+            @Option(name: .customLong("minimum-access-level"),
+                    default: .public,
+                    help: "The minimum access level for declarations to be included")
+            var minimumAccessLevel: AccessLevel
+              
             @Option(name: .shortAndLong,
                     help: "The path for generated report")
             var output: String?
@@ -20,7 +25,7 @@ extension SwiftDoc {
         var options: Options
 
         func run() throws {
-            let module = try Module(paths: options.inputs)
+            let module = try Module(paths: options.inputs, minimumAccessLevel: options.minimumAccessLevel)
             let report = Report(module: module)
 
             if let output = options.output {
diff --git a/Sources/swift-doc/Subcommands/Diagram.swift b/Sources/swift-doc/Subcommands/Diagram.swift
index 50c72443..9e8f4d3d 100644
--- a/Sources/swift-doc/Subcommands/Diagram.swift
+++ b/Sources/swift-doc/Subcommands/Diagram.swift
@@ -11,6 +11,11 @@ extension SwiftDoc {
         struct Options: ParsableArguments {
             @Argument(help: "One or more paths to Swift files")
             var inputs: [String]
+
+            @Option(name: .customLong("minimum-access-level"),
+                    default: .public,
+                    help: "The minimum access level for declarations to be included")
+            var minimumAccessLevel: AccessLevel
         }
         
         static var configuration = CommandConfiguration(abstract: "Generates diagram of Swift symbol relationships")
@@ -19,7 +24,7 @@ extension SwiftDoc {
         var options: Options
         
         func run() throws {
-            let module = try Module(paths: options.inputs)
+            let module = try Module(paths: options.inputs, minimumAccessLevel: options.minimumAccessLevel)
             print(diagram(of: module), to: &standardOutput)
         }
     }
@@ -61,7 +66,7 @@ fileprivate func diagram(of module: Module) -> String {
     }
     
 
-    for symbol in (module.interface.symbols.filter { $0.isPublic && $0.api is Type }) {
+    for symbol in (module.interface.symbols.filter { $0.isIncluded(minimumAccessLevel: module.minimumAccessLevel) && $0.api is Type }) {
         let symbolNode = Node("\(symbol.id)")
         graph.append(symbolNode)
 
diff --git a/Sources/swift-doc/Subcommands/Generate.swift b/Sources/swift-doc/Subcommands/Generate.swift
index 4901dcbc..fc599dfc 100644
--- a/Sources/swift-doc/Subcommands/Generate.swift
+++ b/Sources/swift-doc/Subcommands/Generate.swift
@@ -5,6 +5,8 @@ import SwiftMarkup
 import SwiftSemantics
 import struct SwiftSemantics.Protocol
 
+extension AccessLevel: ExpressibleByArgument { }
+
 extension SwiftDoc {
   struct Generate: ParsableCommand {
     enum Format: String, ExpressibleByArgument {
@@ -30,6 +32,11 @@ extension SwiftDoc {
               help: "The output format")
       var format: Format
 
+      @Option(name: .customLong("minimum-access-level"),
+              default: .public,
+              help: "The minimum access level for declarations to be included")
+      var minimumAccessLevel: AccessLevel
+        
       @Option(name: .customLong("base-url"),
               default: "/",
               help: "The base URL used for all relative URLs in generated documents.")
@@ -42,7 +49,7 @@ extension SwiftDoc {
     var options: Options
 
     func run() throws {
-      let module = try Module(name: options.moduleName, paths: options.inputs)
+      let module = try Module(name: options.moduleName, paths: options.inputs, minimumAccessLevel: options.minimumAccessLevel)
 
       let outputDirectoryURL = URL(fileURLWithPath: options.output)
       try fileManager.createDirectory(at: outputDirectoryURL, withIntermediateDirectories: true, attributes: fileAttributes)
@@ -53,7 +60,7 @@ extension SwiftDoc {
         var pages: [String: Page] = [:]
 
         var globals: [String: [Symbol]] = [:]
-        for symbol in module.interface.topLevelSymbols.filter({ $0.isPublic }) {
+        for symbol in module.interface.topLevelSymbols.filter({ $0.isIncluded(minimumAccessLevel: options.minimumAccessLevel) }) {
           switch symbol.api {
           case is Class, is Enumeration, is Structure, is Protocol:
             pages[path(for: symbol)] = TypePage(module: module, symbol: symbol)
diff --git a/Sources/swift-doc/Supporting Types/Pages/HomePage.swift b/Sources/swift-doc/Supporting Types/Pages/HomePage.swift
index b7a976d8..8e263aba 100644
--- a/Sources/swift-doc/Supporting Types/Pages/HomePage.swift	
+++ b/Sources/swift-doc/Supporting Types/Pages/HomePage.swift	
@@ -18,7 +18,7 @@ struct HomePage: Page {
     init(module: Module) {
         self.module = module
 
-        for symbol in module.interface.topLevelSymbols.filter({ $0.isPublic }) {
+        for symbol in module.interface.topLevelSymbols.filter({ $0.isIncluded(minimumAccessLevel: module.minimumAccessLevel) }) {
             switch symbol.api {
             case is Class:
                 classes.append(symbol)
diff --git a/Sources/swift-doc/Supporting Types/Pages/SidebarPage.swift b/Sources/swift-doc/Supporting Types/Pages/SidebarPage.swift
index 8c98b3af..29e8221c 100644
--- a/Sources/swift-doc/Supporting Types/Pages/SidebarPage.swift	
+++ b/Sources/swift-doc/Supporting Types/Pages/SidebarPage.swift	
@@ -16,7 +16,7 @@ struct SidebarPage: Page {
     init(module: Module) {
         self.module = module
 
-        for symbol in module.interface.topLevelSymbols.filter({ $0.isPublic }) {
+        for symbol in module.interface.topLevelSymbols.filter({ $0.isIncluded(minimumAccessLevel: module.minimumAccessLevel) }) {
             switch symbol.api {
             case is Class:
                 typeNames.insert(symbol.id.description)
diff --git a/Tests/SwiftDocTests/NestedTypesTests.swift b/Tests/SwiftDocTests/NestedTypesTests.swift
index ab2f18c8..35e31d26 100644
--- a/Tests/SwiftDocTests/NestedTypesTests.swift
+++ b/Tests/SwiftDocTests/NestedTypesTests.swift
@@ -23,7 +23,7 @@ final class NestedTypesTests: XCTestCase {
 
         let url = try temporaryFile(contents: source)
         let sourceFile = try SourceFile(file: url, relativeTo: url.deletingLastPathComponent())
-        let module = Module(name: "Module", sourceFiles: [sourceFile])
+        let module = Module(name: "Module", sourceFiles: [sourceFile], minimumAccessLevel: .public)
 
         XCTAssertEqual(sourceFile.symbols.count, 4)