This study illustrated the relationship between swimming, an aerobic activity, and mood. One hundred college students, voluntarily enrolled in beginning or intermediate swimming classes or in lecture-control classes, completed the POMS before and after class. Results of a 5-way ANOVA confirmed that, as predicted, swimmers reported significantly less tension, depression, anger, confusion, and more vigor after exercising than before. Both novice and intermediate swimmers changed significantly more than did controls on all scales except fatigue, while none of the controls' pre-, post-instruction mood changes were significant. The results have implications, similar to those with running, for use in psychotherapy. Despite different social connotations of exercise for women and men, there were no gender differences in the amount of mood change associated with swimming. However, in direct contradiction of existing literature, the women reported significantly less tension-anxiety, depression, anger, and confusion than the men.