Griseofulvin, an antifungal antibiotic agent isolated from Penicillium griseofulvum by Oxford et al.,1 in 1939, has proved to be effective on oral administration in the treatment of certain superficial mycoses. The initial clinical report of Williams, Marten, and Sarkany2 indicated that the drug produced objective improvement and rapid relief of subjective symptoms in patients with Trichophyton rubrum infections and in tinea capitis due to Microsporum audouini. The study by Blank and Roth3 confirmed these results with controlled experiments using a large number of patients with a variety of superficial mycotic infections. The chemical structure of griseofulvin has been established by several investigators.4-8 A method of bioassay against Alternaria solani using a modification of the Botrytis allii hyphal curling assay was described by Gentles9 who also claimed that he could demonstrate the presence of griseofulvin in the hair of guinea pigs previously treated with 30 to 40 mg. per kilogram daily for 23 consecutive days. He proposed the theory that the eradication of mycotic infections by griseofulvin was due to its incorporation in keratin.