The norm of reciprocity requires that we repay in kind what another has done for us. This study examined the degree that social (public) and internal (private) consequences of reciprocation helped to explain both the power and the prevalence of the norm. 166 undergraduates were randomly assigned to conditions in which they were or were not given a small favor, and then were asked to comply with a request. Participants expected that the favor-doer would either know or not know whether they complied with the request. Support was found for both public and private reasons for reciprocation, as the presence of a favor appeared to increase compliance in both public and private conditions. In addition, public compliance was greater than private compliance.