Investigations recently carried out have shown that erythrasma is due to a diphtheroid member of the genus Corynebacterium and that the disease responds to treatment with certain systemically given antibacterial antibiotics (Figs. 1 and 2) (Sarkany, Taplin, and Blank, 1961). The red fluorescence under Wood's light of areas affected by erythrasma, as well as bacteriological studies, have both widened the diagnostic criteria and led to a reappraisal of the disease, its incidence, and significance. Historical In 1862, von Bärensprung first used the term erythrasma to describe "a contagious disease characterized by sharply defined, round or oval patches as seen in pityriasis rubra and confined mainly to the inguinal and axillary regions." He termed the causative organism Microsporum minutissimum. The clinical picture was first delineated by von Bärensprung's pupil, Burchardt, in 1859. While most of the subsequent workers had no doubt that erythrasma was a separate entity (Köbner, 1884; Balzer and