An interpretation of Abadi and Cardelli's first-order function object calculus into a typed π -calculus is presented. The interpretation validates the subtyping relation and the typing judgements of the object calculus and is computationally adequate. This is the first interpretation of a typed object-oriented language into a process calculus. The study intends to offer a contribution to understanding on the one hand, the relationship between π -calculus types and conventional types of programming languages and on the other hand, the usefulness of the π -calculus as a metalanguage for the semantics of typed object-oriented languages. The type language for the π -calculus has Pierce and Sangiorgi's I/O annotations, to separate the capabilities of reading and writing on a channel and variant types. Technical contributions of the paper are the presentation of variant types for the π -calculus and their typing and subtyping properties, and an analysis of behavioural equivalences in a π -calculus with variant types.