Elevated serum transaminases, particularly SGOT, as a result of acetylsalicylic acid (ASA) therapy have been reported in patients with juvenile rheumatoid arthritis (JRA). In order to evaluate the possibilities that these elevated transaminases may result from JRA itself or from concomitant muscle injury, we correlated liver function tests and a specific test for muscle damage, creatine phosphokinase (CPK), with ASA therapy in 37 patients. These JRA patients were evaluated serially; 20 took ASA continuously, 6 took it intermittently, and 11 were on no therapy. Thirty-five healthy children were also studied to establish normal control values for the serum enzyme tests. Mean SGOT and SGPT in the 11 untreated subjects were significantly (P less than.001) higher than normal controls while CPK and alkaline phosphatase (AP) were not elevated. Mean SGOT and SGPT were also significantly (P less than .001) elevated in 20 children receiving ASA continuously; CPK was normal and AP less (P less than .05) than normal. CPK was elevated in 13 patients. Elevation of enzymes was sporadic and there was no correlation with serum salicylate, sex, age, disease duration, type, or activity. We conclude that mild abnormalities of SGOT and SGPT in JRA patients are common, but that they occur sporadically and elevated values appear to be unrelated to ASA therapy.