The Collaborative Ocular Melanoma Study (COMS) is a set of long-term, multicenter, randomized controlled trials. In the trial for patients with tumors of medium size, enucleation and irradiation with an iodine-125 episcleral plaque are compared on the basis of length of remaining life. All randomized patients will be followed for 5 to 15 years or until death. For patients randomly assigned to enucleation, the eye was removed following a standard procedure. For patients assigned to plaque irradiation, the margins of the tumor were located and the dimensions of the tumor were measured by the ophthalmic surgeon. A gold plaque with a plastic seed carrier that contained the proper dosage and configuration of radioactive iodine seeds was sutured to the outside (sclera) of the eye over the base of the tumor. This procedure made possible the delivery of a high dose of radiation to a very localized area (85 Gy [TG-43] to the tumor apex). The plaque typically was removed from the eye after three to seven days. Enrollment was completed in this trial in July 1998 with 1,317 patients enrolled. Clinical follow-up of patients will end in July 2003.