One hundred sixty subjects acted as members of a hypothetical Institutional Animal Care and Use Committee and evaluated five proposals in which animals were to be used for research or educational purposes. They were asked to approve or reject the proposals and to indicate what factors were important in reaching their ethical decisions. Gender and differences in personal moral philosophy were related to approval decisions. The reasons given for the decisions fell into three main categories: metacognitive statements, factors related to the animal, and factors related to the design of the experiment.