Gonads from soft-shell clams, Mya arenaria, were obtained periodically from several Maine and Massachusetts areas to determine the reproductive cycle. Criteria were then established to separate histological preparations of the gonads into categories based on their stage of development in the reproductive cycle. The chronology of this cycle was then determined for samples from several localities on the New England coast. In the northernmost sample areas, clams developed gametes early in the year and spawned from early June to the middle of August. A progressively later gamete development was observed in clams from areas to the south. Clams from Boothbay Harbor, Maine, spawned from late June to late August. Clams from Plum Island Sound, Massachusetts, spawned from July to late September. Although a single annual reproductive cycle was observed in Mya north of Cape Cod, evidence is presented which suggests a biannual cycle south of this boundary.