Author's modification of azomethod and benzidine method were used for determination of the enzyme activity of alkaline phosphatase and peroxidase, respectively, in 62 healthy medical workers. Leucocyte alkaline phosphatase showed a high cytochemical index - 181+-23. Peroxidase was also increased - 234+-9,8. There were no statistically significant differences between the values in physicians, nurses and hospital attendants. The same was true when referred to the duration of service. These studies demonstrate the influence of ionizing radiation on the biochemical characteristics of leucocytes at a time when there were no distinct clinical symptoms and complex morphological changes in the peripheral blood.