Griseofulvin was administered orally in uniform doses of 1,000 mg. daily to 80 patients with dermatomycoses due to Trichophyton mentagrophytes, Trichophyton rubrum, Candida albicans, Epidermophyton floccosum, and Microsporum lanosum. Studies of blood and urine were made at four-week intervals. Six of the ten patients with gastrointestinal side-effects were forced to stop therapy. Success of the medication varied with the site and fungus. Greatest success occurred in patients with rubrum tinea corporis and in those with onychomycosis due to T. rubrum and T. mentagrophytes. Acute dermatophytosis, especially of the soles, toe webs, and groin, showed less prompt response to orally given griseofulvin than to topical therapy. Dermatoses similar to fungus infections did not respond to griseofulvin.