PURPOSE: To evaluate the various forms of clinical presentation, the potential of growth, the risk of functional loss and the possibility of malignant transformation of optic disk melanocytomas in European patients. DESIGN: Retrospective observational case control study. METHODS: Evaluation of 37 cases of optic disk melanocytomas identified in the computer files of the ocular oncology unit of Jules Gonin Hospital to determine the clinical presentation of these tumors and the risk of complications. RESULTS: The tumor was asymptomatic in 28 cases. Visual acuity was normal in 26 cases, subnormal in 10 cases, and in one case it was reduced to 0.1. Visual field defects were observed in 19 cases; the size and extent of the tumor and the degree of papilledema appeared to influence the severity of the visual field defect. Tumor growth was demonstrated in 6 of the 9 cases in which follow-up was for at least six years. In two cases there was presumed malignant transformation that was treated by accelerated proton beam radiotherapy. CONCLUSIONS: Melanocytomas in white Europeans and those of European derivation are rarely symptomatic, have only a moderate effect on visual function and show a low rate of progression over long observation. The risk of tumor progression, although sometimes occurring as much as several years after the initial diagnosis, justifies a cautious approach with long-term regular surveillance of these patients.