Using the specific monoclonal antibody of c-src gene express product, pp60c-src (McAb 327), we studied immunohistochemically in this experiment 35 cases of the esophageal squamous cell carcinomas and 22 adjacent carcinoma tissues. The positive rates of pp60c-src in the squamous cell carcinomas of the esophaguses, the proliferative and the normal squamous epithelis adjacent to the carcinoma were 65.7% (23/35), 100.0% (15/15), and 57.1% (4/7), respectively. There was significant difference among them statistically (P < 0.05). And the express amount of pp60c-src in the esophageal squamous cell carcinoma was higher than those in the proliferative and normal squamous epithelia adjacent to the carcinoma. The positive rates of pp60c-src of the esophageal squamous cell carcinoma with different differentiation grades I, II and III were 80.0% (8/10), 68.4% (13/19), and 33.3% (2/6), respectively. No significant difference was found among them statistically (P > 0.05). The higher the differentiation grade of the esophageal squamous cell carcinoma, the more the express amount of pp60c-src (P < 0.005). The results suggested that the activation and express of c-src gene be associated with the initiation and development of the esophageal squamous cell carcinoma; the express amount of pp60c-src increased in the process and was associated with the differentiation of esophageal squamous cell carcinoma.