To comparatively evaluate the frequency of the neuroendocrine differentiation in the early and in the advanced stage of the disease, 189 gastric carcinomas (67 early gastric cancers and 122 advanced gastric cancers) were studied by immuno-histochemistry using a monoclonal antibody against chromogranin A (CgA). CgA-positive tumor cells were detected in 55 of 189 gastric carcinomas (29.1%). Twenty-two of 67 early gastric cancer (EGC) (32.8%), and 33 of 122 advanced gastric cancer (AGC) (27.0%) were CgA positive. The latter included 23 intestinal type, 8 diffuse type and 2 mixed type tumors. The distribution of CgA-positive tumor cells in most AGC and EGC was focal and the endocrine cells were singularly scattered in the neoplastic glands or, more rarely, grouped in small clusters. CgA-positive tumor cells, moreover, were observed in the lymph node metastases of 12 AGC and 1 EGC. Statistical analysis of data showed no significant difference in the frequency of CgA-positive endocrine cells with regard to the stage of tumor growth, histotype, sex and age. These results indicate that neuroendocrine differentiation is a phenomenon independent of tumor stage, histotype, age, and sex and that CgA-positive cells are present during the whole neoplastic progression.