We report a case with a germline mutation of the p53 gene develpoing both a non-Hodgkin's lymphoma and an astrocytoma. The astrocytoma could be cured by two operations and combined chemotherapy but 33 months after the onset of the disease, he suffered from a diffuse, large cell centroblastic malignant lymphoma of B-cell lineage. In spite of clear rearranged fragments observed with IgH and c-MYC gene probes, we could not diagnose a Burkitt's lymphoma morphologically. The malignant lymphoma was chemoresistant and the patient died of multi-organ failure. He was confirmed to have a germline mutation of the p53 gene by analysis of c-DNA from peripheral lymphocytes and loss of heterozygosity (LOH) of p53 was evident in the lymphoma. The results were suggestive of the Li-Fraumeni syndrome (LFS), a rare autosomal dominantly inherited syndrome with a germline mutation of p53 gene and diverse malignancies, but this could not be confirmed in the present case. Alternatively, a de novo mutation could have been involved.