The pharmacokinetics of cefadroxil suspension were studied in 30 children, 13 months to 12 years of age (mean age, 5.7 years). Average peak concentrations in serum of 11 to 14 mug/ml and of 7 to 10 mug/ml after 15- and 10-mg/kg doses, respectively, were not substantially affected by the feeding status. The serum half-life values were 1.3 to 1.5 h. Cefadroxil was detected in saliva of all children 2 h after 15-mg/kg doses: the levels ranged from 0.17 to 2.6 mug/ml (mean, 0.46 mug/ml). The average concentrations in urine were 1,700 and 2,620 mug/ml at 0 to 2 and 2 to 4 h, respectively, after 15-mg/kg doses. In a randomized controlled study of 50 children with impetigo, cefadroxil was as effective as penicillin G in curing existing lesions and in preventing development of new lesions. Cefadroxil may be useful for therapy of mucocutaneous and urinary tract infections in infants and children.