Adequate social evaluation of an intentional act depends on a specification of the actor's motives, that is, the consequences he or she anticipated when performing the purposeful behavior. Prior work in experimental social psychology has often underestimated the important social functions served by motive statements, including how they influence and regulate social conduct, permit adequate social analysis of purposeful behavior, and project desired identities. Two experiments examined actor-observer differences in the delineation of motives for the positive act of helping another person. In both studies, it was found that actors attributed their behavior largely to positive motives (e.g., to help the other) and minimized nonpositive ones (e.g., to make a favorable impression), while observers' attributions showed little or no differentiation as a function of the valence of the motives. Actors' self-enhancing attributions were somewhat more pronounced when the consequences were large, and occurred under private as well as public assessment conditions. Also, a reversal of the “typical” actor-observer effect was found in that actors attributed more personal than situational responsibility, while observers did the opposite. This pattern occurred under private assessment conditions and was even more pronounced when the actors' interpretations would be public. The results suggest the presence of motivational biases in the interpretation of social events, and are difficult to explain through recourse to the standard “logical” information processing alternatives.