Among 2, 135 consecutive patients with posterior uveal melanoma who were evaluated clinically in the Ocular Oncology Service of Wills Eye Hospital between February 1974 and December 1986, 123 (5.8%) were found to have some degree of extrascleral extension of the tumor. Ten of the 2.135 patients (0.5%) had massive orbital extension we defined as extrascleral tumor having an estimated volume exceeding 1,000 mm3. Three of these patients were characterized by orbital recurrence sometime after enucleation, whereas seven had massive orbital extension as the initial manifestation of the neoplasm with no prior history of enucleation. These cases of advanced orbital extension are presented in detail with emphasis on clinical features, diagnostic problems, pathologic findings, and follow-up observation. Based on our observations, suggestions are made regarding the diagnosis and management of advanced orbital extension of posterior uveal melanoma.