Salicylate is the basic therapy for Kawasaki disease, however its optimal dose is controversial. We investigated the therapeutic efficacy of high dose (100 mg/kg per day, n = 30) versus low dose (30 mg/kg per day, n = 30) salicylate. Duration of fever, SGPT, serum salicylate, plasma thromboxane B2 (TxB2) and 6-keto-prostaglandin F1 alpha (PGF1 alpha) levels were compared before enrollment and on days 4, 7 and 14 of treatment. In the high dose group, duration of fever was significantly shorter than that of the low dose group (3.2 +/- 0.3 versus 5.4 +/- 0.8 days, P less than 0.05), however, SGPT levels were significantly elevated (157 +/- 34 versus 48 +/- 11 IU/1, P less than 0.05). No differences in the incidence of coronary artery lesions were observed (5/30 versus 7/30). Plasma TxB2 production was completely blocked in both groups, and plasma 6-keto-PGF1 alpha levels in the high dose group on day 14 was lower than that in the low dose group (39 +/- 8 versus 159 +/- 65 pg/ml, P less than 0.05). SGPT and plasma 6-keto-PGF1 alpha correlated with serum salicylate concentration. These data suggest that high dose salicylate therapy may be disadvantageous as anti-thrombotic therapy, and supports the notion that low dose therapy is safe in the acute stage of Kawasaki disease.