A 28-year-old woman with an upper nasal iris mass developed secondary glaucoma within a few months of presentation. Although the elevated pressure responded to medical therapy, in the interests of a definitive diagnosis as well as prevention of damage to the trabecular meshwork, surgical management was decided upon. Tumor excision was performed through a double-layered sclerolimbal flap. Light and electron microscopic examinations of the tissue revealed a partially necrotic iris melanocytoma. Six months after surgery, the patient's best corrected visual acuity was 20/30 in the affected eye, and the intraocular pressure was 21 mmHg without therapy. The lens remained clear. The differential diagnosis and management of melanocytomas, particularly the role of biopsy, are discussed.