The following case illustrates an example so often seen in medicine of how treatment for one condition produced improvement in another completely unrelated disease present in the patient, in this case tinea versicolor. This fortuitous observation may lead to further clinical investigation and perhaps better understanding of the pathophysiology of this superficial fungous infection. Report of Case A 29-year-old fish porter at Billingsgate Market, London, came to St. John's Hospital for Diseases of the Skin, complaining of a nonpruritic rash on the chest, which seemed to vary from time to time. Several weeks earlier he had "injured some ribs" on the right side of the chest and was treated at another hospital by application of adhesive tape strapping. This was removed after 2 weeks. When seen 3 weeks after removal of the strapping, he presented a widespread, erythematous scaly eruption on the chest and the upper arms (dark areas in