The mechanisms by which mood states influence attitude judgments in persuasion settings are delineated in terms of current dual-process theorizing. With an emphasis on mechanisms that may operate when the evaluative implications of message content are ambiguous. In a preliminary test of hypotheses concerning such circumstances, college-aged subjects were put into a happy or sad mood and then read a message containing unambiguous strong, unambiguous weak, or ambiguous arguments, which was attributed to a highly credible source (heuristic cue) When message content was ambiguous, sad (as compared to happy) subjects' attitudes were more influenced by heuristic processing, and their message-related thoughts were biased by the heuristic cue. These and other results are discussed within a dual-processing framework, and compared to other social cognition theorizing on the impact of affect on social judgment.