Two randomized, double-blind, vehicle-controlled, multicenter studies assessed the efficacy and safety of a new terbinafine 1% solution for the treatment of interdigital tinea pedis and tinea corporis or tinea cruris (tinea corporis/cruris). Patients with interdigital tinea pedis applied terbinafine 1% solution or vehicle twice daily for 1 week with 7 weeks of follow-up (N=153), and patients with tinea corporis/cruris applied terbinafine 1% solution or vehicle once daily for 1 week with 3 weeks of follow-up (N=66). Efficacy was assessed mycologically and clinically at the end of treatment and throughout follow-up. In the tinea pedis study, 66% of patients were effectively treated with terbinafine compared with 4% of the group treated by vehicle (P<.001; Mantel-Haenszel test). In the tinea corporis/cruris study, treatment was effective in 65% of the terbinafine group compared with 8% of the vehicle group (P<.001). There were no significant differences in the frequency of cutaneous adverse events between the 2 groups in either study. We conclude that one week of therapy with terbinafine 1% solution is highly effective, superior to vehicle, and safe for use in superficial fungal infections.