In brief: Despite increasing evidence that regular aerobic exercise yields many benefits for patients with arthritis, patients often are advised to curtail physical activity. Findings from studies of patients with either rheumatoid arthritis or osteoarthritis who participated in an aerobic exercise program show that the subjects made significant gains in aerobic capacity, functional status, muscle strength, and other aspects of performance. In addition, they improved in subjective aspects that might have a positive impact on quality of life, including pain tolerance, joint pain, mood, and social activity. The authors discuss some questions that remain unanswered and present guidelines for physicians who wish to prescribe aerobic exercise for their arthritis patients.