Mutations in the p53 gene were detected in 27 of the 107 (25%) cases of non-Hodgkin's lymphoma (NHL), examined by assaying the transcriptional activity of p53 in yeast. A relatively high mutation rate of p53 was observed in B-cell intermediate-grade NHL and in T-cell high-grade immunoblastic NHL, in contrast to the relatively low mutation rate observed in other pathological classifications. However, retrospective analyses of all 76 cases revealed that the survival profile and therapeutic responses were very similar in NHL patients bearing lymphomas with a mutant p53 or with the wild-type p53 even within the subclasses characterized by frequent p53 mutation. In patients with high-intermediate grade tumors, the median survival period was 24 months in mutated p53 cases and 14 months in wild-type cases. Complete remission (CR) was observed in 9 of the 17 patients (53%) with mutated forms of p53 and 18 of the 35 patients (51%) with wild-type p53 genes. Our analyses of NHL patients revealed that the presence of p53 mutations may influence pathological grades of NHL, but did not strongly correlate with poor prognosis or reduced chemo/radiosensitivity in NHL. Hence, mutations of p53 do not serve as a prognostic, or chemo/radiosensitivity marker in NHL.