The staining method of the nucleolar organizer regions (NOR) with colloidal silver azotate applied on paraffin section was used by us in cases of malignant uveal melanoma classified according to Callender histopathological types. The following AgGNOR values were found: in spindle shaped malignant melanomas type A and B the AgNOR values ranged between 4.6 and 8.2 (mean level 6.54); in epitheloid malignant melanomas AgNOR, values between 5.3 and 23 (mean level 10.96), and in mixed malignant melanomas AgNOR, values between 4.8 and 15 (mean level 8.63). The AgNOR levels found in the present investigation would correspond to the clinical prognosis known for the various types of malignant uveal melanoma, that is, A and B spindle shaped forms with lower AgNOR levels and more favorable prognosis than for the epitheloid and mixed forms with higher AgNOR levels and poorer prognosis.