A two-tiered model of group influences on individual choice behavior is developed and evidence relevant to the model is reviewed in this paper. The model consists of two parts: a model of individual choice, and models of group influence on components of the individual choice model. The model of individual choice is based on the elimination-by-aspects choice model of Tversky. This choice model suggests two sources of influence that groups might have on individuals: messages sent by other group members might change the value an individual attaches to a given choice criterion; or, messages sent by other group members might change the individual's estimate of the probability that a given alternative possesses a certain attribute. Models of both sources of group influence are developed, and implications and testing of the model are discussed. (Author)