Abstract: Objective 　To investigate whether there is abnormal expression of p53 protein in multiple primary malignant tumors. Methods 　The expression of p53 protein in multiple primary malignant tumors from 21 patients with double malignant tumors was studie using immunohistochemical staining with antibody against this protein. Results 　In 21 patients, the expression of p53 protein in double tumors was 9 cases (42. 85%, 9/21), the expression of p53 protein in single tumor was 9 cases (42. 85%, 9/21), Three other patients were negative for p53 protein. Conclusion 　Tumor suppressor gene p53 may be playing a crucial role in the development of multiple primary malignant tumors. The significance of these findings warrants further investigations.