A 59-year-old man presented with a well-demarcated, tender ulcer at the base of the penile shaft that had been present for approximately five years. The ulcer had been responsive neither to topical antibacterials, antifungals, and glucocorticoids nor to oral acyclovir. A biopsy specimen showed an intra-epidermal neoplasm consistent with extramammary Paget disease (EMPD) based on light microscopy and immunohistochemistry. Patients with EMPD require extensive medical evaluation because of its association with adnexal carcinoma and visceral malignant conditions. Evaluation should include a full body skin and lymph node examination, colonscopy, cystoscopy, and sex-specific studies including pelvic and breast examinations, with imaging for women and prostate examination with prostate specific antigen levels for men. Close monitoring after treatment is important because of the recognized risk of recurrence and malignant conditions.