This article develops a framework that encompasses past two-sided persuasion research and incorporates additional theory and research on optimal arousal and attitude toward the ad to provide explanations for inconsistencies in previous findings. In particular, explanations are provided for the following: (1) when credibility gains will be enhanced, (2) when refutation is needed, (3) how the message should be structured (in terms of amount and placement of negative information), and (4) what types of attributes should be discounted (in terms of importance, type, and correlation with other attributes). In addition, directions for future research are discussed. Copyright 1994 by the University of Chicago.