The loss of alleles at loci on specific chromosomes in some malignant tumors, such as retinoblastoma and Wilms' tumor, suggests that recessive mutations are important in their oncogenesis. We postulate that similar mechanisms may be involved in the formation of uveal melanomas. We studied alleles at autosomal loci in uveal melanoma cells and in the constitutional cells from 19 patients who developed the tumors. We observed loss of alleles only at loci on chromosome #2. This suggests that recessive alleles at some chromosome #2 locus may be important in the oncogenesis of uveal melanomas.