Five continuous cell lines have been established from 29 ocular melanomas and maintained for periods ranging from 3 to 9 years in medium identical to that in which 3 concomitantly studied lines of cutaneous melanoma cells were cultured as controls. The long-term problems to be overcome in establishing uveal cell lines are related to cell-doubling times which ranged from 72 to 432 hr, and plating efficiency, which ranged from 0.5%-6.5%. Tumors and cell lines were found to contain melanosomes. The morphology of uveal cells during the early subcultures exhibited multiple changes. Two different established cell lines were obtained from one ciliary-body tumor. Biochemical studies revealed markers of melanogenesis and neuroendocrine compounds. Cytogenetic studies revealed chromosomal abnormalities that differed between uveal and conjunctival melanomas.