A garbage collector collects at least a generation of a dynamically allocated heap in increments. In each increment, it identifies references located outside a collection set that refer to objects that belong to the collection set, and it evacuates the objects thus referred to before it reclaims the memory space that the collection set occupies. In some collection increments, references to collection-set objects are located both inside and outside the generation. The collector locates all such references, both those inside the generation and those outside it, before it evacuates any objects in response to any of them. By doing so, it is able to reduce the cost of locating references and evacuating objects.