The economics of growing Tridacna gigas giant clams inter-tidally is examined on the basis of experience with culture at Orpheus Island Research Station, James Cook University, Northern Australia. Even at a price as low as $3 per kg for clam meat on the farm, it is shown that profitable culture can be expected. At a real rate of interest of 10 per cent per year, the most profitable duration for growing clams for meat production is to 11 years of age. The farm is assumed to acquire 100,000 seed clams of approximately one-year each year. Analyses indicate that the real rate of return on funds used can be expected to exceed 10 per cent. Financial analysis of cash flows indicates that the payback period (for the finance needed) for a new farm being set up for giant clam culture is relatively long and initially the debt/asset ratio of the farm is likely to be high. The length of the payback period is significantly affected by the price of clam meat and the rate of interest. Assuming an annual real rate of interest of 10 per cent, payback is complete at the end of 12 years if clam meat sells for $7 per kg; at the end of 13 years if it sells for $5 per kg and at the end of 16 years if it sells for $3 per kg. While these payback periods may seem to be long, there are many types of commercial projects which have even longer payback periods.