The purpose of the present study was to compare the personality characteristics of 93 participants engaged in aerobics, circuit training, or Tai Chi for a period of six months or more using the Motivational Style Profile (MSP: Apter, Mallows, & Williams, 1998). Stepwise discriminant function analysis with Wilks' Lambda statistical criterion was employed in separate statistical analyses with the ten MSP subscales as predictors of membership of three exercise groups. Motivational Style Profile dominance scores produced non-significant discriminant functions. However, the MSP subscales produced significant discrimination between the three exercise groups. The most accurate prediction of correct group membership was 66.7% for aerobics, with 64.7% accuracy for circuit training, and 51.7% of correct classifications for Tai Chi. Discriminant function 1 separated the Tai Chi group from the other two exercise groups and discriminant function 2 differentiated the circuit training group from both Tai Chi and aerobics groups. The Tai Chi group had high levels of alloic-mastery and low levels of both autic-mastery and arousal-seeking. The circuit training group had high levels of negativism and arousal-seeking. The aerobics group had low alloic-mastery, and high autic-mastery in comparison to the Tai Chi group and lower levels of negativism and arousal-seeking than the circuit training group. The findings are important because they identified differences between the three activity groups rather than between exercise activity and non-activity groups. Also, MSP subscale scores were more sensitive discriminators of exercise group differences than their derived dominance values.