The technical possibility of farming giant clams has been established by the Micronesian Mariculture Demonstration Center (MMDC), by the Australian Centre for International Agricultural Research (ACIAR) and other organizations. Enterprises have already been established to farm giant clams commercially. However, the extent of market demand for giant clams and their components has not been established. Clearly the economics of farming will depend both on demand factors and cost considerations. To determine the likely demand for farmed clams is not an easy task. Such markets as have existed in the past have been based on natural stocks. Supply from these has been uneven and has not been sustained due to overharvesting. Pre-existing markets for natural clam stocks and their components are likely to provide at best an imprecise guide to the demand for farmed clams. For example, natural stocks have been insufficient or protected in some areas such as Australia which has meant that a local market for clam meat has not been established. Clam meat for consumption would be an experiential good for Australians and Westerners and, one suspects, many Asians, including Japanese. Markets exist for giant clams as aquarium specimens and for their shells. Surveys have recently been undertaken in Australia to determine the size of the Australian market for these end-uses and the main findings are reported. The market for clams for meat is likely to be difficult to gauge. In many markets the product would, in effect, be a new product, and for example, new product cycles might apply. In the past attempts have been made to use international trade statistics and the market for possible substitutes, e.g. scallops as a guide to the potential market. These approaches all have drawbacks. As for substitutes, it would for example seem that substitutes for clam meat would vary with the age and method of preparation of the clam. Younger clams, say on the half-shell, can be used as entrée items and might, up to a point compete with other entrée items such as oysters. Older clams are usually separated into muscle and mantle components which can be frozen and which lend themselves to retail sale in blister packs. Evidence about likely commercial demand remains fragmentary but available data will be reviewed. Given the data problems and the likelihood that to some extent ‘supply creates its own demand’, standard economic analysis may be of limited value in determining the demand for clam meat. Some observations will also be made on other possible uses of and markets for giant clams and on subsistence demand for clams.