This paper presents a filter model for π-calculus and shows its full abstraction with respect to a ‘may’ operational semantics. The model is introduced in the form of a type assignment system. Types are related by a preorder that mimics the operational behaviour of terms. A subject expansion theorem holds. Terms are interpreted as filters of types: this interpretation is compositional. The proof of full abstraction relies on a notion of realizability of types and on the construction of terms, which test when an arbitrary term has a fixed type.