The argyrophilic nucleolar organizer region (AgNOR) of 100 cancer cells from biopsy specimens of esophageal squamous cell carcinomas in 98 surgically treated cases was examined, using a silver colloid staining technique on biopsy specimens. The number of AgNOR per nucleus (AgNOR number) was higher in the more advanced groups with regard to the length of the tumor (P less than 0.01), the depth of penetration (P less than 0.05), and lymph node metastasis (P less than 0.01). The survival of the patients with a high AgNOR number (greater than or equal to 6) was significantly poorer than those with either a medium range AgNOR number (4 less than or equal to-less than 6) (P less than 0.05) or a low AgNOR number (less than 4) (P less than 0.01). In the multivariate analysis including conventional clinicopathological factors, the AgNOR number was found to be one of the independent and significant variables (P less than 0.01). Because the AgNOR method is simple and can be applied to paraffin-embedded sections, the AgNOR number may provide potential benefit in the pretherapeutic assessment of malignant potentiality in esophageal carcinoma.