To investigate the expression of P53 protein in the premalignant lesion and carcinoma of laryngeal epithelium, the authors used DO-7, an antibody to wild and mutant type P53 protein. Eleven cases of simple hyperplasia of epithelium (SHE), 32 cases of atypical hyperplasia of epithelium (AHE) and 42 cases of laryngeal squamous cell carcinoma (LSCC) were examined by ABC technique. The results showed that the overexpression of P53 protein were 0%, 31.25% and 52.38% in SHE, AHE and LSCC, respectively. The positive rate of P53 protein were 0%, 33.33% and 75.00% in mild, moderate and severe AHE, respectively. In well, moderately and poorly differentiated carcinomas of larynx, the positive rates were 62.50%, 76.92% and 15.39%, respectively. There were highly significant differences (P < 0.01). No correlation was found between the P53 protein overexpression and the clinical stages, neck lymph node metastasis, local recurrence and, survival of LSCC. The results suggest that the overexpression of P53 protein may play a role in the pathogenesis and development of LSCC.