A 23-year-old white woman presented with a pigmented ciliary body mass in the left eye. The tumor appeared to transilluminate when observed with indirect illumination. Clinically the tumor was considered to represent either a malignant melanoma or a cyst and was excised by iridocyclectomy. Electron microscopic examination established the smooth muscle nature of the tumor. The literature on this unusual tumor is reviewed. Furthermore, this report serves to emphasize the value of iridocyclectomy in the diagnosis and treatment of ciliary body tumors.