[en] The percentage of CD2⁺, CD4⁺, CD8⁺ and HNK-1⁺ cells in peripheral blood was investigated in persons occupationally exposed to very low doses of ionizing radiation. Investigations were carried out by monoclonal antibodies and flow cytometry. While significant effects of age and smoking habits on the relative number of CD8 cells and CD4/CD8 ratios could be established, no influence of the very low radiation exposure on the profile of lymphocytic T cells in blood was found, except a very slight effect on the relative number of CD2⁺ cells. (author)