One hundred two patients with active erosive rheumatoid arthritis (RA) without malalignment or deformities (median disease duration, 14 months) entered a double-blind, randomized study to compare the effects of 50 mg gold sodium thiomalate (GST) with 15 mg methotrexate (MTX) administered intramuscularly for 12 months. Roentgenograms of hands, wrists, and forefeet were taken at baseline and after 6 and 12 months, and 32 joints were evaluated according to Larsen. Sixteen of 50 patients in the MTX group were withdrawn; one patient in the MTX group died of cerebral bleeding that was not related to treatment. Thirty-four GST patients and 44 MTX patients were evaluated for efficacy. Thirty-eight joints were counted. The number oftender and swollen joints, the Lansbury articular index, morning stiffness, activities of daily living (ADL) score, and erythrocyte sedimentation rate improved significantly in both groups without statistical intergroup differences. After 12 months, there was a significant deterioration of the mean Larsen index and the number of joints with erosions without intergroup difference. However, the radiological progression was retarded significantly during the second 6-month period in the gold group, whereas this effect was less pronounced in the MTX group. At 12 months, the progression rate was the same in both groups.