Sixty-four patients with clinically and mycologically diagnosed tinea corporis and tinea cruris were randomly allocated to receive either 250 mg of oral terbinafine once daily or 500 mg of griseofulvin once daily for 2 wks. Patients in each group were well matched for age, gender, clinical features and type of dermatophytes. Clinical and mycological control tests (KOH wet mount and culture) were performed before treatment, at the end of treatment and 4 wks after stopping treatment. In the majority of cases, the infecting agent was identified as Trichophyton rubrum (53/64). The remainder comprised Trichophyton mentagrophytes (8/64) and Epidermophyton floccosum (3/64). After 2 wks of therapy, there was no significant difference in mycological response in the terbinafine group (90.3%) and griseofulvin group (80.7%). The clinical response in both groups was the same. At 6 wks' follow-up, the mycological cure in terbinafine and griseofulvin group was 87.1 and 54.8 per cent, respectively (P < 0.05). The clinical response of the terbinafine group was also significantly higher than in the griseofulvin group. A higher relapse rate was observed in the griseofulvin group than in the terbinafine group. No serious side effects were reported in either group. The result showed that oral terbinafine was more effective than oral griseofulvin in the treatment of tinea corporis or tinea cruris.