In ihis paper, we design and analyze a growable multicast ATM switch. It can grow to a large size since both cell routing and contention resolution are designed to distribute over switch elements, and the switch structure is modular. The output ports arc partitioned into groups to permit sharing of routing paths. The concept of group routing helps reduce an order of magnitude of sufitch elements. A two-stage switch architecture is described to illustrate our design principle. The switch can be easily expanded io a larger site b y using more stages. The performance analysis of Ihe switch in terms of cell loss rate, cell dclay, mean queue length, mean waiting time, and throughput is conducted using the M/Geoni/l model. Experimental results show that the proposed ATM switch not only meets the ATM performance requirements either for unicasting or multicasting but also uses fewer switch elements and has less delay than other comparable switches.