The purpose of this study was to explore the determinants of exercise behavior in adults. A total of 400 adults completed self-report questionnaires. The questionnaires included a demographic data sheet, past 3-month exercise questionnaire, interpersonal influences scale, self-rated health sub-index, self-rated abilities for health practice exercise subscales, and exercise benefits/barriers scale. Results showed that 35.3% reported that they never performed any type of exercise; and only 29.0% practiced more than 90 minutes each week in the past 3 months. The results indicated that all of the variables predicted 15% of the variance in exercise behavior. Of all the variables, sex, interpersonal influences, perceived health status, and perceived exercise self-efficacy made significant contributions to the prediction of exercise behavior. Path coefficients ranged from 0.10 to 0.19.