The effectiveness of laughter in reducing physiological and psychological measures of stress is compared with relaxation training and control groups. Personality factors of sense ofhumor and use ofhumor to cope äs well äs group size are also compared. Subjects were 74 College students randomly assigned to either a humorous or control videotape, or an audiotaped relaxation program. While laughter was not found to be äs effective äs relaxation training in reducing physiological measures of stress, it did appear to reduce psychological measures. Personality factors were found to be significantly correlated with stress reduction, especially with women.