This paper shows how to perform concurrent and distributed automatic garbage collection of objects possessing their own thread of control. The relevance of garbage collection and active objects to distributed applications is briefly discussed and the specific model of active objects used in the paper is explained. The collector is comprised of independent local collectors, one per node, and a distributed global collector. The mutator (application), the local collectors and the global collector run concurrently. An important part of this paper is the detailed presentation of the algorithms necessary to achieve correct concurrent operation among the collectors and between the collectors and the mutator. The collector builds on previous algorithms for taking snapshots in distributed systems and for detecting termination.>