Twenty-nine patients with active rheumatoid arthritis receiving long-term oral weekly methotrexate (MTX) therapy were studied to determine the extent of their hepatic architectural changes. Liver biopsies (n = 101) were performed in all patients before the initiation of MTX therapy, after 2 years, and annually thereafter (mean duration of therapy 53 months). The hepatic histologic grade (5-point scale) in 25 patients increased (worsened) (mean +/- SEM change 0.84 +/- 1.02; P = 0.001). Fibrosis, confirmed by trichrome staining, developed in 14 of 27 patients (52%). A history of alcohol consumption prior to starting MTX correlated significantly with subsequent worsening of the liver biopsy grade (r = 0.55, P = 0.0054). Alcohol intake prior to study entry, elevated weight at MTX initiation, and dose and duration of MTX were significantly associated with the development of fibrosis. Elevations in serum aspartate aminotransferase levels at 29-53 months of therapy correlated with the increase in hepatic histologic grade at the 3-year biopsy (r = 0.50, P = 0.04) and 4-year biopsy (r = 0.58, P = 0.03). We conclude that long-term MTX therapy in rheumatoid arthritis patients results in a statistically significant worsening in hepatic histologic grade, with common development of mild fibrosis. We do not consider these changes to be clinically significant at present.