BACKGROUND: Information about orbital malignancies in Papua New Guinea (PNG) is limited to reports published 20 years ago. The present retrospective study was performed to establish the pattern of malignant orbital lesions occurring in PNG and to see whether the pattern is any different from that reported in the earlier series and in other countries. Papua New Guinea is special in that it has a large and relatively homogenous population unaffected,to a large extent, by contact with the'outside world'. METHODS: The records of 176 proven cases of orbital malignancy treated between 1975 and 1996 were studied with respect to type of tumour, age, gender; mode of presentation and, where possible, treatment and its outcome. RESULTS: Orbital tumours were found to be uncommon relative to other malignancies. The most common orbital tumour encountered in the present study was orbital extension of retinoblastoma (40.3%). These tumours were all unilateral and were associated with a very high mortality. No bilateral or familial cases were seen. Squamous cell carcinomas were the second most common tumours (25.6%) and were seen in young adults (average age 36.6 years). Basal cell carcinomas (9.1%) occurred later (average age 54 years) and were more common in the lighter-skinned Southern Highlanders and expatriates. The other malignancies seen included lacrimal gland tumours (3.4%), malignant melanomas (4.5%), lymphomas (3.4%), rhabdomyosarcomas (1.7%), meibomian cell carcinomas (1.7%) and soft tissue sarcomas. CONCLUSIONS: Most patients presented late and the mortality rate was high. This could also reflect the relative paucity of ophthalmic and oncological services in the country as well as psychosocial attitudes to disease. Many patients live far from medical services and may be treated by traditional healers before coming to a hospital.