One hundred and twenty patients with symptomatic rheumatoid arthritis (RA) or osteoarthritis (OA) in weight bearing joints (RA = 40; OA = 80) performed subjective maximal graded exercise tests on a motor driven treadmill. Disease related measures were also assessed. Findings from this sample indicated that people with arthritis were significantly impaired in exercise tolerance, flexibility and biomechanical efficiency. Significant differences between diagnoses appeared on a number of disease related measures; however, there was little correlation between disease related measures and exercise tolerance. Women demonstrated a greater aerobic impairment than men; and women with RA had a greater aerobic deficit than women with OA.