The stages of change construct of the Transtheoretical Model (TTM) has been proposed for examining exercise adoption. Studies investigating the construct validity of the stages of change for exercise have used physical activity of moderate or higher intensity as operationalization criterion. Since it has been shown that physical activity of lower intensity also provides health benefits, we investigated whether the stages of change appropriately address lower intensity physical activity. Data with respect to the stages of change as well as behavior, intention and self-efficacy associated with mild, moderate, and strenuous exercise were collected in a sample of 467 males and females aged 20 - 85. Results show that the stages of change can be distinguished by moderate and strenuous but are not consistent with mild exercise. Implications for future research utilizing the stage of change conceptualization are discussed and development of new stage assessment instruments for mild exercise is recommended.