In this randomized double-blind trial, two new antifungal compounds were compared in patients with interdigital or more extensive forms of tinea pedis. Two weeks of oral treatment with either terbinafine, an allylamine and new chemical entity, 250 mg daily, or itraconazole 100 mg daily, was given to 366 patients (184 terbinafine, 182 itraconazole). Of 13 patients who did not return after the first visit, 11 were lost to follow-up (five on terbinafine, six on itraconazole) and two reported adverse events. Another nine patients (three on terbinafine and six on itraconazole) were excluded because it was uncertain to which group they were randomized. A central laboratory performed both the mycology and safety tests. In 355 patients who received the study medications and were available for analysis of side-effects, 18 out of 179 (10.0%) in the terbinafine group and 10 out of 176 (5.7%) in the itraconazole group reported adverse events. No new clinically significant laboratory abnormalities were seen after treatment. At week 8 the efficacy analysis in 117 patients with mycologically confirmed dermatophyte infections (51 on terbinafine, 66 on itraconazole) showed that clinical symptoms were absent or minimal in 94.1% of the terbinafine and 72.7% of the itraconazole group (P = 0.0095); mycology was negative in 86.3% of the terbinafine and 54.5% of the itraconazole group (P = 0.0002). With terbinafine, negative mycology at week 8 was 81.3% in the interdigital and 88.6% in the more extensive forms of tinea pedis; with itraconazole mycology was negative in 65.0% and 50.0% of patients, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)