The paper considers the economics of giant clam mariculture in the South Pacific, with special attention to Fiji. Approximate economic and biological data are used in order to determine the internal rate of return from a small maricultural activity. Under certain conditions, it is found that clam mariculture could be profitable. Important factors affecting profitability are found to be 1) post-harvest drip loss, 2) seed clam price, 3) output price and 4) mortality rates of clams. It is also stressed that it appears unlikely that villagers will undertake clam farming as a subsistence activity. Villagers' interest lies in finding new commercial activities to supplement subsistence production.