Of 11 patients with acute rheumatic fever, 9 were treated with a total daily salicylate dosage of 3,6 g or less, 1 patient required a total daily dosage of 5,4 g and another required 9,0 g daily. Six of the 11 patients had elevated serum transaminase levels, and all were asymptomatic. The elevated transaminase levels appear to bear a direct relationship to the serum salicylate level, and a serum salicylate level of 19,2 mg/100 ml appears to be the critical point. In 5 out of the 6 patients with elevated transaminases, the serum salicylate level exceeded 19,2 mg/100 ml, while in the 5 patients with normal transaminases the serum salicylate level did not exceed 19,2 mg/100 ml. Also, in 10 of the 11 patients eosinophilia was noted, but this decreased despite continued or increased salicylate administration. A narrow margin thus appears to exist between therapeutic serum salicylate levels and hepatotoxic levels, and serial serum transaminase estimations are advocated in patients on long-term salicylate therapy.