Forty patients, randomly assigned to an experimental and a control group, participated in a double-blind study to assess the effectiveness of acupuncture in reducing chronic pain associated with osteoarthritis. The experimental group received treatment at standard acupuncture points, and the control group at placebo points. Analysis before and after treatment showed a significant (P less than 0.05) improvement in tenderness and subjective report of pain in both groups as evaluated by two independent observers and in activity by one observer. Comparison of responses to treatment between the two groups showed no significant (P greater than 0.05) difference. Thus, both experimental and control groups showed a reduction in pain after the treatments. These results may reflect the natural course of illness, and various attitudinal and social factors.