Studies of immunosenescence have led to a detailed knowledge of immune system dysfunctions in the ageing human being. Apoptosis seems to be one of the process regulating an immune response after the antigenic stimulation. We examined whether commonly used methods of assessing apoptosis in the elderly human subject produce comparable results to young subjects. PBMC of young and elderly volunteers were isolated from the venous blood and cultured for 6 or 24h with antigens of anti-influenza vaccine or PMA. The intensity of apoptosis was measured using the annexinV test, flow cytometric evaluation of DNA content (sub-G1 peak in DNA histograms), ‘ladder’ by DNA gel electrophoresis, and fluorescence microscope. Apoptosis in 6h-lasting cultures of the elderly was more intense in annexinV test, while it was decreased assessing subG1 peak. Additionally, in the aged group, those changes were associated with cell cycle arrest. Our results suggest that the apoptosis after the stimulation with the vaccine antigens seems to be some kind of activation-induced cell death (AICD). Different patterns of apoptosis after stimulation may be associated with the cell cycle arrest of the PBMC in the elderly.