We studied the effectiveness of short-term treatment of tinea corporis and tinea cruris with oral terbinafine at 250 mg/day for 2-3 days. The treatment on an open study basis consisted of two groups: the first group (n=17) was given 250 mg/day for two consecutive days, and the second group (n=24) was given the same dose for three consecutive days. No patient was treated topically. Effectiveness was evaluated at the end of the second week both clinically and mycologically (KOH examination and culture). In the two-day group, five cases showed an excellent response, three had a good response and nine had a fairly good response. Patients with good response or better comprised 47.1% of the total, while those with excellent response stood at 29.4%. The negative mycological examination ratio was 47.1%. In the three-day group, 12 cases showed an excellent response, four a good response while eight had a fairly good response. Patients with a good response or better comprised 66.7% of the group, while cases with an excellent response comprised 50.0%. The negative mycological examination ratio stood at 66.7%. The overall effectiveness evaluation showed no statistically significant difference between the two treatment groups in the Wilcoxon's rank sum test. No side effect was observed in either group. These findings showed that terbinafine therapy of tinea cruris is effective even with a short-term treatment of 2-3 days at a small dose.