Jocaml is a system for mobile agents built inside the Objective-Caml language. Jocaml eases the development of concurrent, distributed and mobile agent based applica-tions, by expressing useful distribution abstractions using a small set of simple but powerful primitives taken from the Join-Calculus. The system provides total transparency for migration, application states (after migration, all threads resume their execution in the state before migration), communications (communication channels with other agents are kept during migration) and composition (sub-agents migrate with their parent agent). Other features of the Jocaml system are mobile objects with transparent remote method invocation, distributed garbage collection, failure detection and execution efficiency. Jocaml has already been used in several applications, such as a mobile editor, some distributed games and a distributed implementation of Ambients. This paper describes the Jocaml programming model and language, its current implementation and some interesting applications.