Previous findings of correlations between mood and personality variables were noted. It was suggested that the establishment of a causal relationship was crucially important, not merely to the understanding of how mood is related to personality but to the conceptualization of mood as a source of error in personality measurement as well. A prior attempt to establish a causal role for mood failed, but may have done so for methodological reasons. The present study investigated the influence of a mood manipulation on personality measures. There was also an opportunity to replicate prior correlational findings independent of the effect of the mood manipulation. College students were asked to think of happy, sad, or affectively neutral events and then filled out several personality measures. A manipulation check confirmed that different moods were induced by this procedure. The prior correlations between mood and personality variables were replicated, but the mood manipulation did not affect any of the personality measures. The implications of these results for personality measurement and for the relation between mood and behavior were discussed.