Twelve children with severe systemic juvenile chronic arthritis, all requiring high dose corticosteroids, have been admitted to a pilot study to evaluate the effect of low-dose methotrexate (mean dose: 8.5 mg/M2) on disease activity over a 6 month period. Definite improvement occurred in 4 children, allowing reduction of the steroid dose in 2 cases. Two children showed an acute flare of disease activity during the treatment period and in three, steroids had to be increased. Overall, side effects were rare with a rise in transaminases only occurring once. MTX blood levels taken on 14 occasions in 8 children documented absorption in all cases with a mean level of 3.45 x 10(-7) mol/l on a mean dose of 9 mg/M2. Low-dose MTX appears to be a safe drug in the short term treatment of severe systemic JCA with beneficial effect in about a third of patients. Long-term controlled trials will be needed to evaluate its role in the treatment of systemic disease as well as side effects.