Background: Ofuji's disease, also referred to as classic eosinophilic pustular folliculitis, is a rare dermatosis of unknown origin for which there is no uniformly effective treatment. Objective and Methods: Twenty patients with Ofuji's disease (classic eosinophilic pustular folliculitis) evaluated in our department from January 1978 to June 1999 were studied clinically and histopathologically. Laboratory data, treatments, and clinical courses were evaluated in 12 of these individuals. Results: Nissl modified staining revealed moderate increases of mast cells around hair follicles and sebaceous glands in all 20 patients; the majority of the infiltrating mast cells were tryptase-positive and chymase-negative. Eight of 11 patients treated with oral indomethacin responded completely. Conclusions: Indomethacin is an effective therapy for Ofuji's disease. Tryptase-positive and chymase-negative mast cells might play some role in the pathogenesis of Ofuji's disease. (J Am Acad Dermatol 2002; 46:827-33.)