ABSTRACT.Purpose: To evaluate the efficacy and the safety of uveal melanoma transretinal biopsy using 25-gauge vitrectomy system. Methods: At the patient's request of a tissue diagnosis, nine posterior uveal melanomas treated by proton-beam therapy were biopsied during the insertion of tantalium markers. Results: The diagnosis was uveal melanoma, confirmed in all cases using cytological (7 of 9) and histological analysis (2 of 9). Immunocytochemistry was performed on all samples (9 of 9). In eight of nine patients, minor postoperative vitreous haemorrhages were seen, which resolved in 1 day. No other ocular complications were noticed. Conclusion: Uveal melanoma biopsy using 25-gauge vitrectomy system is a valuable procedure to confirm the diagnosis, with adequate sample and low ocular morbidity.