diff --git a/.gitattributes b/.gitattributes
index 2b2d87f..863b8f0 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -4,4 +4,5 @@
 # Always use lf for F# files
 *.fs text eol=lf
 *.fsx text eol=lf
-*.fsi text eol=lf
\ No newline at end of file
+*.fsi text eol=lf
+*.expected text eol=lf
\ No newline at end of file
diff --git a/src/FSharp.Analyzers/Codes.fs b/src/FSharp.Analyzers/Codes.fs
index dc54e46..4623313 100644
--- a/src/FSharp.Analyzers/Codes.fs
+++ b/src/FSharp.Analyzers/Codes.fs
@@ -5,3 +5,6 @@ let StringEndsWith = "GRA-001"
 
 [<Literal>]
 let StringStartsWith = "GRA-002"
+
+[<Literal>]
+let StringIndexOf = "GRA-003"
diff --git a/src/FSharp.Analyzers/StringAnalyzers.fs b/src/FSharp.Analyzers/StringAnalyzers.fs
index 5570e42..03a554f 100644
--- a/src/FSharp.Analyzers/StringAnalyzers.fs
+++ b/src/FSharp.Analyzers/StringAnalyzers.fs
@@ -140,9 +140,10 @@ module StringAnalyzers =
             else
                 fsharpType.GenericArguments |> Seq.map visit |> String.concat " -> "
 
-        visit mfv.FullType = expectedSignature
+        let actualSignature = visit mfv.FullType
+        actualSignature = expectedSignature
 
-    [<CliAnalyzer>]
+    [<CliAnalyzer "String.EndsWith Analyzer">]
     let endsWithAnalyzer (ctx : CliContext) : Async<Message list> =
         invalidStringFunctionUseAnalyzer
             "EndsWith"
@@ -157,7 +158,7 @@ module StringAnalyzers =
             | _ -> false)
             (hasMatchingSignature "System.String -> System.Boolean")
 
-    [<CliAnalyzer>]
+    [<CliAnalyzer "String.StartsWith Analyzer">]
     let startsWithAnalyzer (ctx : CliContext) : Async<Message list> =
         invalidStringFunctionUseAnalyzer
             "StartsWith"
@@ -171,3 +172,18 @@ module StringAnalyzers =
             | SingleStringArgumentExpr _ -> true
             | _ -> false)
             (hasMatchingSignature "System.String -> System.Boolean")
+
+    [<CliAnalyzer "String.IndexOf Analyzer">]
+    let indexOfAnalyzer (ctx : CliContext) : Async<Message list> =
+        invalidStringFunctionUseAnalyzer
+            "IndexOf"
+            Codes.StringIndexOf
+            "The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload."
+            Warning
+            ctx.SourceText
+            ctx.ParseFileResults.ParseTree
+            ctx.CheckFileResults
+            (function
+            | SingleStringArgumentExpr _ -> true
+            | _ -> false)
+            (hasMatchingSignature "System.String -> System.Int32")
diff --git a/src/FSharp.Analyzers/StringAnalyzers.fsi b/src/FSharp.Analyzers/StringAnalyzers.fsi
index 49bd96d..69cdf62 100644
--- a/src/FSharp.Analyzers/StringAnalyzers.fsi
+++ b/src/FSharp.Analyzers/StringAnalyzers.fsi
@@ -3,8 +3,11 @@ namespace ``G-Research``.FSharp.Analyzers
 open FSharp.Analyzers.SDK
 
 module StringAnalyzers =
-    [<CliAnalyzer>]
+    [<CliAnalyzer "String.EndsWith Analyzer">]
     val endsWithAnalyzer : ctx : CliContext -> Async<Message list>
 
-    [<CliAnalyzer>]
+    [<CliAnalyzer "String.StartsWith Analyzer">]
     val startsWithAnalyzer : ctx : CliContext -> Async<Message list>
+
+    [<CliAnalyzer "String.IndexOf Analyzer">]
+    val indexOfAnalyzer : ctx : CliContext -> Async<Message list>
diff --git a/tests/data/string/indexof/Constant String - Single Argument.fs b/tests/data/string/indexof/Constant String - Single Argument.fs
new file mode 100644
index 0000000..61ab7fa
--- /dev/null
+++ b/tests/data/string/indexof/Constant String - Single Argument.fs	
@@ -0,0 +1 @@
+"foo".IndexOf("p")
diff --git a/tests/data/string/indexof/Constant String - Single Argument.fs.expected b/tests/data/string/indexof/Constant String - Single Argument.fs.expected
new file mode 100644
index 0000000..4a4c32c
--- /dev/null
+++ b/tests/data/string/indexof/Constant String - Single Argument.fs.expected	
@@ -0,0 +1 @@
+GRA-003 | Warning | (1,6 - 1,13) | The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload.
diff --git a/tests/data/string/indexof/Function call - Single Argument.fs b/tests/data/string/indexof/Function call - Single Argument.fs
new file mode 100644
index 0000000..d9b6e16
--- /dev/null
+++ b/tests/data/string/indexof/Function call - Single Argument.fs	
@@ -0,0 +1,2 @@
+let f () = "f"
+"g".IndexOf(f())
diff --git a/tests/data/string/indexof/Function call - Single Argument.fs.expected b/tests/data/string/indexof/Function call - Single Argument.fs.expected
new file mode 100644
index 0000000..c659fc3
--- /dev/null
+++ b/tests/data/string/indexof/Function call - Single Argument.fs.expected	
@@ -0,0 +1 @@
+GRA-003 | Warning | (2,4 - 2,11) | The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload.
diff --git a/tests/data/string/indexof/Prefixed Value - Single Argument.fs b/tests/data/string/indexof/Prefixed Value - Single Argument.fs
new file mode 100644
index 0000000..63de87d
--- /dev/null
+++ b/tests/data/string/indexof/Prefixed Value - Single Argument.fs	
@@ -0,0 +1,4 @@
+module A =
+    let b = "b"
+
+A.b.IndexOf("b")
diff --git a/tests/data/string/indexof/Prefixed Value - Single Argument.fs.expected b/tests/data/string/indexof/Prefixed Value - Single Argument.fs.expected
new file mode 100644
index 0000000..8425d45
--- /dev/null
+++ b/tests/data/string/indexof/Prefixed Value - Single Argument.fs.expected	
@@ -0,0 +1 @@
+GRA-003 | Warning | (4,4 - 4,11) | The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload.
diff --git a/tests/data/string/indexof/Value - Single Argument.fs b/tests/data/string/indexof/Value - Single Argument.fs
new file mode 100644
index 0000000..deb7b20
--- /dev/null
+++ b/tests/data/string/indexof/Value - Single Argument.fs	
@@ -0,0 +1,2 @@
+let a = "a"
+a.IndexOf("a")
diff --git a/tests/data/string/indexof/Value - Single Argument.fs.expected b/tests/data/string/indexof/Value - Single Argument.fs.expected
new file mode 100644
index 0000000..affccf7
--- /dev/null
+++ b/tests/data/string/indexof/Value - Single Argument.fs.expected	
@@ -0,0 +1 @@
+GRA-003 | Warning | (2,2 - 2,9) | The usage of String.IndexOf with a single string argument is discouraged. Signal your intention explicitly by calling an overload.