A 23-year-old man presented witha firm plague-like penile mass with pain and deviationon erection, suggesting Peyronie's disease. Biopsy was erroneously interpreted asconformatory. Irradiation was the one mode of therapy which gave temporary subjective relief. Extension of the mass and focal gangrene led to rebiopsy 6 years later. Epithelioid sarcoma was present microscopically, and was also found on re-examination of theoriginal biopsy. Partial penectomy was performed, but pulmonary metastasis had alreadyoccurred. He was treated with chemotherapy and radiotherapy and is now alive with disease 2 years later. The diagnosis of possible penile sarcoma, although rare, must be considered in patients with symptons suggesting Peyronie's disease, especially if the lesion continues to enlarge.