The main objective of this study was to determine whether motivational and volitional variables identified in the health action process approach (HAPA) model can be used to successfully differentiate people with multiple sclerosis (MS) in different stages of change for exercise and physical activity. Ex-post-facto design using multiple discriminant analysis was used. Participants were 215 individuals with MS. The outcome variable was measured by the Physical Activity Stages of Change Instrument, along with motivational and volitional measures (severity, action self-efficacy, outcome expectancy, risk perception, perceived barriers, intention, maintenance self-efficacy, action and coping planning, and recovery self-efficacy). Participants in the precontemplation, contemplation, and action groups can be maximally separated by two significant canonical discriminant functions, volition and motivation. The action group can be differentiated from other groups based on high group mean (centroid) score on the volition function, and the precontemplation group can be differentiated based on low group means on both the motivation and volition functions. The contemplation group can be differentiated based on high centroid score on the motivation function. Research findings of this study support the concept of stage-matching exercise and physical activity intervention. The HAPA framework can be used to design health promotion behavioral interventions for people with MS in vocational rehabilitation. (Contains 2 tables.)