This study explores differences in exercise and walking behavior among subjects who reported temporary or long-term illnesses or injuries serious enough to have limited physical activities. The study is primarily concerned with specifying similarities and differences in correlates of vigorous exercise and walking among illness/injury groups in comparison to a healthy sample. Subjects in the analysis (N = 2,053) were drawn from a multiwave mailed survey of a probability sampling of the adult population residing in households in San Diego, California. Although differences were found in correlates of walking and vigorous exercise among the groups, self-efficacy, the belief that one is able to perform specific activities, was the most powerful and statistically significant correlate of both walking and vigorous exercise among all groups.