Apoptosis-related proteins might play an important role in the pathogenesis and sensibility to the chemotherapeutical drugs in patients with non-Hodgkin's lymphoma (NHL). In our study we tried to find out the relation between the expression of CD95/Fas/Apo-1 antigen and clinical outcome of NHL patients. We have measured 24-hour spontaneous apoptosis of peripheral lymphocytes on flow cytometer using specific monoclonal anti-CD95 mouse antibodies in 54 patients aged 19-76 years. Fas expression proved to be a significant prognostic factor in predicting overall survival (OS) because in CD95- (<25%) patients OS was 7% vs. CD95+ with 30%. After grouping of patients by IPI score there was no significant difference between Fas negative and positive cases (IPI 1 - 50% vs. 68%; IPI 2 - 50% both), although in unfavorable risk-groups the OS values differed according to the CD95 expression (IPI 3 - 20% vs. 70%; IPI 4 - 11% vs. 50%). So we conclude, that Apo-1 positive expression appears to be predictive of good overall survival as an independent prognostic parameter, as in association with IPI criteria.