We immunohistochemically investigated Epstein-Barr virus (EBV)-positive and negative 31 malignant lymphomas (MLs) for p53 protein using a monoclonal antibody which is expressed on a wild type and mutant human p53 protein. We evaluated the presence of mutations in exons 5 to 8 of the p53 gene using single-strand confirmation polymorphism analysis. Overexpression of p53 was detected in 13 out of 31 cases (41.9%) of MLs. However, we have documented the presence of structural alterations of the p53 gene in six cases of MLs. The presence of EBV infection in MLs was statistically unrelated to p53 protein overexpression. Excellent correlation was found between p53 immunoreactivity and histologic types of MLs. Even though the reason for discrepancy between p53 gene mutation and p53 protein overexpression remains unclear, p53 protein overexpression may be involved in the process of malignant transformation regardless of EBV infection in MLs.