The aim of the study was to characterize the leukocytes (L) from the peripheral blood of centenarians.The study involved 39 subjects aged 100 years and older (group S – 33 females and 6 males) as well as 40 young healthy individuals aged 20–30 years (group K – 35 females and 5 males). In all of them, the quantitative and qualitative analysis of L from blood smear was performed.