The data used in this study was based on the Annual Economic Survey of Offshore Fisheries and Aquaculture in Taiwan from 2000 to 2003. A model using data envelopment analysis (DEA) was specified and estimated. The results of the DEA showed that a return to scale decreased in hard clam (Meretrix lusoria) aquaculture production in Taiwan, and the mean technical efficiency was 56.06%. Tobit analysis showed that those farmers with higher education and who used higher culture densities attained higher technical efficiencies. The study results suggest that hard clam aquaculture in Taiwan should increase the culture density to an appropriate level, but expanding the culture scale was deemed to be unsuitable.