Studied the effects of varying belief similarity on a behavioral variable (aggression) and interpersonal attraction. 48 male undergraduates competed with a pseudo-opponent on a RT task. On each of several trials Ss set varying levels of shock which they wished the opponent to receive if the latter lost on that trial, and received shocks the opponent set for them if they lost. S's shock setting constituted a direct measure of aggression. Ss competed against an opponent who was either similar or dissimilar in attitudes, and who was either aggressive or nonaggressive, and then evaluated the opponent on several scales. Results show that only aggression of the opponent affected Ss' counteraggression. Both opponents' aggressiveness and belief similarity affected attraction. It is suggested that the common sense assumption that attraction mediates aggression may be incorrect. The 2 variables may be independent with different sets of determinants. The everyday observation of co-occurrence of liking and aggression may be due to the simultaneous activation of their separate independent variables. (18 ref.) (PsycINFO Database Record (c) 2016 APA, all rights reserved)