Forty patients with rheumatoid arthritis (RA) were enrolled in a double blind study of 26 weeks duration designed to compare the efficacy and safety of parenteral methotrexate and sodium aurothiomalate (GSTM) in the treatment of RA. All the patients had active RA and none had previously received gold, D-penicillamine or immunosuppressive therapy. Patients were randomized to receive weekly intramuscular (IM) injections of either methotrexate 10 mg or GSTM 50 mg. Two patients taking methotrexate and 7 taking GSTM were withdrawn before 26 weeks. Methotrexate was as effective as GSTM as measured by numbers of swollen or tender joints, morning stiffness, grip strength, pain scale and erythrocyte sedimentation rate. Five patients taking methotrexate and 11 taking GSTM presented side effects (p = 0.05). Total number of adverse reactions was 5 for the methotrexate group and 15 for the GSTM group (p less than 0.01). Our data suggest that low dose IM methotrexate is less toxic and as effective as GSTM for the treatment of RA during the first 6 months of therapy.