A garbage collector collects a generation of a dynamically allocated heap in a computer's memory incrementally. A collection set within the generation is associated with each collection increment. The collector reclaims for reuse the memory space occupied by any collection-set object not reachable by a reference chain that extends from outside the collection set. The collector monitors the total amount of allocation that occurs within the generation between collection increments, and it bases the collection-set size on those allocation amounts.