We report the clinical and histological findings in a tumor of the pigmented ciliary epithelium. The tumor was detected because it had caused a unilateral cataract, and it was removed by local resection because a malignant melanoma could not be excluded. The diagnosis was established by light microscopy, and additional immunohistochemical and detailed ultrastructural studies were performed. The so-called foam cells which are considered typical of these adenomas appear to be mostly light microscopic artifacts and had no ultrastructural equivalent in the sections examined from our tumor. Our results also strongly support the hypothesis that no true glandular elements are formed and that, apart from the neoplastic tissue architecture, most of the pathological findings are related to melanosomes.