Nucleolar organizer regions (NORs) can be stained by a simple one-step silver technique; the black dots formed are termed AgNORs. Often AgNORs are tightly clustered, appearing as one silver-stained nucleolus (AgNu). We have assessed this technique as a possible prognostic indicator for thick (greater than 3.0 mm) primary cutaneous malignant melanoma (CMM). Three groups were studied: (A) seven thick CMM that had not metastasized 8-20 years after excision; (B) three thick CMM that developed metastases 6-9 years after excision; and (C) twelve CMM that presented with metastases or developed them within 4 years of excision. Two methods of counting silver-stained black dots in nuclei were employed: one method counted easily discernible black dots consisting of AgNus and dispersed AgNORs; the other attempted to count actual AgNORs both dispersed and clustered within AgNus. Scores per nucleus by the first method were 1.5-6.7 in group A, 1.1-2.6 in group B, and 1.4-5.4 in group C. AgNOR counts by the second method were 6.2-13.0 in group A, 5.4-8.9 in group B, and 5.3-10.5 in group C. No significant difference was present between groups for scores by either method. Due to the subjectively, technical difficulty, non-reproducibility, and tedium associated with the second method of attempting to count individuals AgNORs, the first method is recommended. It is concluded that this technique is of no value in predicting prognosis for CMM.