Yes, order of files in a project matters. If Things.fs contains type Foo and Main.fs uses it, then the project must look like MyProj |- Things.fs |

Yes, order of files in a project matters. If Things.fs contains type Foo and Main.fs uses it, then the project must look like MyProj |- Things.fs |- Main.fs Visual Studio has a few functions to manage this order. The benefit is faster compilation, because F# requires recursive types to be declared together, such as type Foo = A of Bar | B and Bar = {Baz: Foo} this doesn't really come up that much.