Dishman (1994) has described the need to better understand the "natural history" of exercise patterns and how they are developed and maintained. To that end, this investigation examined the level of association of stage of exercise (Transtheoretical Model) with exercise identity and exercise efficacy. Theory suggests that exercise identity and exercise efficacy should explain progression and maintenance of exercise behavior in later stages of the change process. Data were collected (during the first week of classes) from a convenient sample of 575 students enrolled in two elective health-studies courses, emergency aid and personal health. Ninety-four per cent of the survey participants self-identified as Caucasian and 69% were female. Average age was 20.5 years with a range of 18 to 47 years. Stage of exercise behavior was assessed using a five-item related to regular exercise behavior and intentions (Marcus, Selby, Niaura, & Rossi, 1992). Exercise identity was measured by the sum of nine Lickert-type items (Anderson & Cychosz, 1994) designed to measure the extent to which exercise was descriptive of the concept of self (a=.94). Exercise efficacy (Marcus, et al., 1992) was assessed by the sum of seven Likert-type items designed to measure confidence in one's ability to overcome barriers to exercise participation (a=.83). A MANOVA revealed a statistically significant exercise stage effect, F(6,1130)=46.41, p<.001, and a statistically significant gender effect, F(2,564)=8.01, p<.001. No statistically significant stage by gender interaction effect was displayed. Univarite results for exercise stage were significant for both exercise identity, F(3,565)=104.48, p<.001 and exercise efficacy, F(3,565)=52.31, p<.001 while results for gender were significant only for exercise efficacy, F(1,565)=16.05. p<.001, with males showing higher exercise efficacy scores than females. A stepwise regression analysis was performed with exercise stage as the dependent variable and exercise identity and exercise efficacy as predictor variables. Results indicated that exercise identity and exercise efficacy were significantly associated with exercise stage (R2=47%). Exercise identity score entered first and explained 44% of the variance in exercise stage. Exercise efficacy was entered next and made a statistically significant addition of 3%. These data provide insight into the sociopsychological process underlying maintenance and expansion of exercise activities. These data suggest that Exercise Identity increases through the change process, peaking in the "maintenance" stage. This is consistent with the theory that the development of this social identity and self-perceptions of exercise efficacy may combine to sustain and perpetuate behavior. Keyword(s): health promotion, physical activity