The prognostic significance of age was studied in 372 patients with diffuse large B-cell non-Hodgkin's lymphoma, in relation to the prognostic factors of overexpressed BCL2 and p53 oncoprotein. Overexpression of BCL2 and p53 oncoprotein was defined when more than 50% of the tumor cells showed positive staining. The data were analyzed with respect to the age groups < 65 and > or = 65 years of age. There was a trend for BCL2 overexpression to occur significantly more often among patients older than 65 years of age (P = 0.065). Patients with BCL2 overexpression showed significantly inferior disease free survival rate, but only for patients younger than 65 years (log-rank test P = 0.0002), and the overexpression showed also an independent prognostic significance (P < 0.001). With respect to overexpressed p53 a significant difference was reached for complete remission rate (P = 0.01) and 5-year survival rate (log-rank test P = 0.04), again only for the younger age group. When the analyses were repeated for the older patients who had been treated adequately, the same lack of significance was found, both for BCL2 and p53. This study demonstrates that the negative prognostic value of overexpressed BCL2 and p53 protein is not of concern for patients older than 65 years of age. Among elderly patients the International Prognostic Index score seems the predominant risk factor for inferior prognosis.