In an open study, oral administration of thalidomide to 7 female patients with classic or definite rheumatoid arthritis, in doses ranging from 6.9 to 15 mg/kg/day, led to clinical improvement within several weeks. In 4 women, remission lasted long after discontinuation of the drug. All patients showed normalization or marked reduction of the erythrocyte sedimentation rate, and several showed a significant decrease in rheumatoid factor titer. Adverse side effects included drowsiness, constipation, and edema of the lower limbs, which disappeared after discontinuation of the drug.