Single somatic cells, including fibroblasts, myelomas, and hybridomas, proliferate normally when trapped between a plastic dish and a disc of polyester cloth. Contact between the overlay and the plastic for 8-16 days results in identical colony patterns on the cloth and the plate. When several cloth discs are simultaneously stacked over Chinese hamster ovary cells, three or four-high resolution colony copies can be generated from a single master dish. The colonies on the cloth can be analyzed by radiochemical methods [Esko, J. D. & Raetz, C. R. H. (1978) Proc. Natl. Acad. Sci. USA 75, 1190-1193] or by "replica plating" to a new disc. The use of polyester cloth, singly or in stacks, has several major advantages over previous techniques for somatic cell replica plating, including: (i) broad applicability to diverse cell lines such as fragile membrane mutants of Chinese hamster ovary cells and relatively nonadherent myelomas or hybridomas; (ii) the possibility of generating multiple copies of the same colony population, allowing simultaneous analysis for several enzymes or cellular components; and (iii) superior resolution and transfer efficiency in copying colony patterns from one surface to another. The remarkable capacity of animal cell colonies to proliferate upward through "polyester stacks" may reflect chemotropic movement of individual cells and opens new approaches to somatic cell genetics.