The patient was a 57-year-old woman who initially consulted our department on May 31, 2002 with a chief complaint of other dermatoses. The initial examination demonstrated deformation of approximately 1/3 of the inner part of the nail plate in the right hallux, in addition to brown discoloration and keratin hypertrophy under the deformed nail plate. KOH-prepared direct microscopy revealed the presence of large round spores and hyphae. Since colonies similar to those of Trichophyton rubrum were obtained by culture, daily administration of terbinafine (125 mg/day) was initiated from June 17, 2002 based on a suspicion of tinea unguium induced by T. rubrum. However, the morphology of the colonies began to change toward a brown powder-like configuration after 2-3 weeks of culture, and band forms were also detected by slide culture, resulting in the diagnosis of onychomycosis induced by Scopulariopsis brevicaulis. From August 6, 2002, the dose of terbinafine was increased to 250 mg/day, which was maintained until November 22, 2002. When the patient visited our department approximately 2 months later, KOH-prepared direct microscopy revealed that she was still positive for S. brevicaulis. Therefore, terbinafine (250 mg/day) was administered again for 1 month from April 25, 2003, followed by a judgment of complete healing on July 4, 2003. Thereafter, there was no recurrence of onychomycosis up until January 29, 2005.