SummaryThe authors reviewed their experience with 524 secondary orbital tumor cases diagnosed histopathologically during 1963–1993. Secondary tumors constituted 48.0% of all orbital biopsies during the same period. There were 186 (35.5%) cases with eyelid tumors, 146 (27.9%) cases with intraocular tumors, 137 (26.1%) cases with conjunctival tumors, 26 (5.0%) cases with nasopharyngeal tumors, 22 (4.2%) cases with sinus carcinomas, 3 (0.6%) cases with intracranial meningiomas, 3 (0.6%) cases with esthesioneuroblastomas, and 1 (0.2%) case with chordoma. The three most frequent tumors making secondary orbital invasion were basal cell eyelid carcinoma (129 cases; 24.6%), squamous cell conjunctival carcinoma (125 cases; 23.8%), and retinoblastoma (123 cases; 23.5%). Squamous cell carcinoma, from various sites of origin, was the most frequent histopathologic tumor variant, accounting for 215 (41.0%) cases. Exenteration was performed on 334 (63.7%) of 524 cases with secondary orbital invasion. The ignorance of many lid and conjunctival lesions until the advanced stages, which could otherwise be easily treatable, caused blindness and life-threatening complications under our conditions. Orbital invasion from ocular retinoblastoma and uveal malignant melanoma led to a markedly poor prognosis, again related to the late presentation of many patients. Lack of health consciousness, inadequate primary surgery, and/or insufficient follow-up were the main reasons for secondary orbital invasion in many tumor cases.