Recent attempts to improve the influence of social marketing have often focused on behavioral strategies, largely neglecting the concept of attitude. This is understandable given the weak performance of attitudinal variables as a predictor in past studies of proenvironmental behavior. However, we suggest that part of the reason for the poor association between attitudes and such behavior is the possibility that many altruistic acts such as recycling are subject to affective influences that may not be fully captured by commonly employed attitude measures. We also suggest that attitude strength might moderate the extent to which affective reactions account for additional variance in behavior. Specifically, it is predicted that affect is more important for weak than for strong attitudes. Empirical results are presented to support these suggestions. © 1994 John Wiley & Sons, Inc.