Discusses the influence of expectancy on interpersonal processes and behavior. The effect of perceiver expectancy concerning a target individual is examined with regard to 3 phenomena: the target’s behavior, the processing of the target’s behavior by the perceiver, and the target’s self-perception. Findings related to target behavior influences are categorized in terms of experimenter–subject interactions, teacher–student interactions, casual interactions, and bargaining and negotiation. Studies concerned with the perceiver’s processing of target behavior are discussed in relation to perceptual and behavioral confirmation/disconfirmation of expectancies. The psychological and sociological models for self-concept change are described.