The relative efficacy of various types of treatment in preventing metastatic uveal melanoma is unclear. We have performed a phase I-II non-randomised trial to determine if patients with large (greater than 15 mm in diameter or greater than 5 mm in thickness) uveal melanomas would benefit from pre-enucleation irradiation. Twenty-eight patients were treated between 1978 and 1983 by means of 5 X 5 cm anterior wedge pair ports on a 4 me V linear accelerator. Each patient received five 4 gray (400 rad) fractions over a five-day period for a total of 20 Gy. Enucleation was performed by a single surgeon within five days after treatment. The mean follow-up of the patients was 24 months (range 7-54 months). All melanomas were histologically confirmed. Four patients (14%) have developed metastatic tumour with a mean interval between diagnosis and death of 25 months. No significant perioperative or long-term morbidity was observed.