The purpose of this study was to examine the determinants of physical activity behavior in adults with cognitive disabilities (CD). Physical activity participation is a complex and dynamic behavior that is affected by a variety of social, psychological, environmental, and physiological factors. The impact of disability experienced by adults with CD may create physical activity determinants that are unique to this population. Research indicates that adults with CD are inactive and at risk for development of chronic diseases associated with inactivity (Frey, 1997; Pitetti & Campbell, 1991; Pitetti, Rimmer, & Fernhall, 1993). However, there have been no documented attempts to identify the factors that influence physical activity in this population. Investigating physical activity determinants in this population is complicated because standard survey instruments used for people without CD can be leading due to the a priori nature of survey questions. Qualitative methodology is a more appropriate choice for learning about physical activity participation of individuals with CD. Two women and three men with mild CD volunteered to participate and each participant provided informed consent. Two participants were diagnosed with Down syndrome and three with idiopathic mental retardation. One participant resided with parents, one with a caregiver, and three independently. Three were employed full-time and two part-time. Three participants were involved in segregated recreation activities and two were not engaged in any type of formal activity program. The data source was an in-depth interview conducted with each participant consisting of open-ended questions concerning daily routines and physical activity. Spradley’s (1979) ethnographic framework was used for the interview questions. Analysis of the interviews using constant comparison resulted in the following themes: Physical requirements of job (e.g., being on feet and lifting), physical activity outside of work (e.g., club dancing), participation in Special Olympics, access to opportunities for physical activity and exercise, obstacles to physical activity and exercise (e.g., time and money), and encouragers of physical activity and exercise (e.g., looking good and being with friends). While participation patterns and incentives for physical activity of individuals with CD closely resemble those of adults without CD, they seem to be exacerbated by factors related to their disability.