The purposes of this study were to explore the factors that influenced adherence to an exercise program for older adults, and compare differences in motivation, efficacy expectations, health status, age, functional performance, and falls between adherers and nonadherers. A combined qualitative and quantitative design was used. Participants included 23 of the 24 members of an existing walking group, with an average age of 81 +/- 7.2 years. Fourteen (60%) participants did not adhere to walking, while 9 (40%) adhered. Those that adhered had fewer functional limitations due to their health, (F = 7.7, p < .05), better functional performance (F = 4.0, p < .05), stronger self-efficacy expectations related to exercise (F = 4.3, p < .05), and fewer falls (F = 4.4, p < .05). Six major themes were identified that impacted adherence: a) beliefs about exercise; b) benefits of exercise; c) past experiences with exercise; d) goals; e) personality; and f) unpleasant sensations associated with exercise. Interventions that focus on teaching older adults about the benefits of exercise, establishing appropriate goals, and decreasing unpleasant and increasing pleasant sensations associated with exercise may be useful to improve adherence to a regular exercise program.