The objective of this study was to compare the argyrophil nucleolar organizer region (Ag-NOR) counts of conjunctival nevi and melanomata and to compare the efficacy of this method in their differential diagnosis. Nine histologically diagnosed conjunctival nevi and three conjunctival malignant melanomas were studied. Representative sections were stained using the AgNOR technique. Fifty cells of each melanocytic lesion were randomly selected without knowing their histologic diagnosis. The AgNORs were visualized at a magnification of x1000. They consisted of clusters >1 micron in diameter and of satellites <1 micron in diameter, which were counted and recorded for each cell separately. The mean AgNOR count for the nevi was 1.12 clusters and 1.72 satellites per cell, while the count for the melanomas was 1.6 clusters and 6.8 satellites per cell. These results are statistically significant. There was no overlap between the number of AgNOR clusters and satellites in conjunctival nevi and melanomas, indicating that the AgNOR count might be a useful tool in distinguishing benign from malignant conjunctival melanocytic lesions.