Clinical and laboratory data in 124 patients with rheumatoid arthritis treated with methotrexate (MTX) were retrospectively reviewed over the initial 2 years after the start of treatment. Clinical improvement occurred in 103 (83%) patients after 12 weeks of treatment. At 2 years of followup, 60 patients (48%) continued to receive MTX with sustained clinical benefit. It has been discontinued in 64 (52%) patients (adverse drug reactions in 38, lack of clinical benefit in 15, and miscellaneous reasons in 11). Patients with adverse drug reactions had higher initial serum creatinine and blood urea nitrogen values than patients without adverse drug reactions.