In this study, we investigated endoscopic biopsy material consisting of 76 esophageal squamous cell carcinomas after immunostaining with three p53 monoclonal antibodies (PAb 1801, PAb 240, and DO-7). p53 protein was detected in 51.3% of the tumours. The protein was not expressed in the normal mucosa. Statistical analysis of follow-up data on 54 patients showed that high p53 levels were to a significant degree frequently associated with unfavorable treatment response (p < 0.053) and death (p < 0.05); whereas expression of the protein was not correlated with tumor differentiation, DNA ploidy, S phase value, EGF-R expression, or Ki67 index. The results of these studies suggest that in cases of esophageal carcinoma, immunohistochemical detection of p53 protein can be used to predict outcome.