We studied 80 children with tinea capitis without kerion to define the epidemiology and clinical characteristics of tinea capitis and to compare the therapeutic efficacy of griseofulvin and ketoconazole for treatment of this disorder. Patients ranged in age from 2.1 to 11 years (median, 5.2 years). Trichophyton tonsurans (74%), Microsporum canis (13.5%) and Trichophyton mentagrophytes (2.7%) accounted for 90% of the infections. Pretreatment KOH slide preparations were positive in 69% of patients with alopecia and in only 29% of those with diffuse scale with little hair loss. Sixty-three patients were randomly assigned to receive ketoconazole (5 mg/kg/day) or griseofulvin (15 mg/kg/day). The treatment groups were comparable with regard to age, sex, duration of lesions prior to treatment and type of lesions. The percent of patients with positive cultures on therapy at 4, 6, 8, and 10 weeks and the mean time to a sterile culture were significantly larger (P less than 0.01) in ketoconazole (8 weeks) than in griseofulvin-treated (4 weeks) patients. The time for complete scalp clearing was significantly longer in patients who received ketoconazole (median, 108 days) compared with those who were treated with griseofulvin (median, 60 days) (P = 0.01).