One hundred twenty-six patients with rheumatoid arthritis (RA) were treated with weekly low doses of methotrexate (MTX) for a mean period of 36.8 months (range 13-110 months). The overall probability of continuing with MTX therapy was 72% at 2 and 3 years, 67% at 4 years and 65% at 5-7 years. Seronegative patients had a higher probability of continuing therapy than seropositive patients (P < 0.05). Out of the whole group, 8% showed no improvement, 16% showed mild improvement, 30% showed moderate improvement, and 45% experienced marked improvement. Eight patients (6%) of the latter group achieved complete clinical remission. In the course of the follow-up period there was a significant decrease in the mean daily dosage of prednisone and NSAIDs. Minor side effects were common (68%), but therapy was discontinued in only 27 patients (21%) because of major complications. In most of them (25 out of 27) these occurred within the first 24 months of therapy. Although malignancy was revealed in 5 patients during the follow-up period, its occurrence did not differ from expected rates.