We studied the immediate effects of rapid freezing on 19 variously sized uveal melanomas that were subjected to cryoenucleation using liquid nitrogen and a cryoring by light and electron microscopy and tissue culture. The freezing time and the temperature of 11 lesions were recorded. The light microscopic finding of an intranuclear clear center with peripheral displacement of clumped chromatin against the nuclear membrane was suggestive of intranuclear ice crystal formation but did not indicate cellular death of the tumors. The major ultrastructural changes, including plasmalemmal breaks, dissolution of cytoplasmic matrix, and damage to various organelles, however, suggested acute necrosis in tumors not exceeding 7 mm in elevation. Failure of the melanoma cells to grow in tissue culture and positive staining with trypan blue support the contention of tumor death. The late effects of rapid freezing were also evaluated in another case of uveal melanoma. The eye was enucleated six months after cryopexy. Histopathologic findings showed that the tumor was necrotic. Failure of the neoplasm to regress (noted clinically) was related to edema and inflammatory infiltrates.