Fifty-one patients, thirty-nine women and twelve men, with Pityrosporum folliculitis are described. This investigation clearly demonstrates that Pityrosporum folliculitis is a real entity. The diagnosis is based primarily on the clinical picture, direct microscopy, histopathology, and the effect of antimycotic treatment. The typical patient is a woman of 30 years with itching follicular papules and pustules localized to the upper trunk or upper arms. Direct microscopy reveals round yeast cells and sometimes even hyphae. In biopsy specimens, abundant round budding yeast cells and occasionally hyphae are seen in a dilated follicle. Yeast growth is obtained only on lipid-enriched media. Twenty-five patients were treated with selenium sulfide shampoo, twelve with 50% propylene glycol in water, and ten with topical econazole cream with good results. Cure or marked improvement was seen after 3 to 4 weeks, but symptoms and lesions recurred if treatment was not continued intermittently. Predisposing factors such as occlusion and greasy skin are probably important, and future studies should focus on fungal hypersensitivity, quantitative variations in the number of Pityrosporum orbiculare, lipid composition of the skin, and extended epidemiologic data.