ACIAR has been funding research into giant clam mariculture since 1983/84. By the time this research terminates in 1991, ACIAR will have provided $3.2m in research funds. The benefits of this ACIAR-sponsored research are assessed from several different points of view applying diverse types of project appraisal. Market-related cost-benefit analysis (CBA) similar to that used by Davis, Oram and Ryan (1987) is applied to estimate benefit-cost ratios. A benefit-cost ratio of at least 4.8 on ACIAR's research expenditure is estimated, when a zero rate of discount is applied. But even when a positive rate of discount is applied, the benefit-cost ratio can be expected to exceed unity. Conway's agroecosystem approach to project appraisal is also applied. The development of giant clam mariculture is found to be meritorious in terms of sustainability, to have good stability properties and potentially favourable income distribution effects. The level of returns from giant clam mariculture are still uncertain but there are prospects of above normal returns, even though financial returns are not immediate. Thus the development seems to rate positively applying Conway's approach. This is also true for extended CBA and sustainability supplemented CBA. Evolutionary-type appraisal of the ACIAR-supported research is favourable in terms of the diversity of research approaches tried, the diversity of possible economic developments based on the mariculture, the scope for small scale production and the appropriateness of technologies developed. A range of benefits have been or can be expected from this project for Australia and for less developed countries, and these are listed. The; project will not only yield tangible direct contributions to economic production but indirect non-materialistic (nonconsumptive) benefits, e.g. conservation benefits in terms of existence, option and b quest values. Conservation benefits are a major advantage of this project, but even without these it would be justified in economic terms.