Standard (hemogram, routine biochemical indices) and non-standard hematological parameters reflecting monocytic-macrophagal system (MMS) function and antioxidant defense were investigated in 140 subjects who had worked in radionuclide-contaminated zone after the Chernobyl accident. As shown by measurements of iron serum metabolism, lysozyme, total interferon, CIC, chemiluminescence of venous blood mononuclear leukocytes, MMS in 50% of them underwent negative changes in suppressed antioxidant defense. Standard hematological findings registered abnormalities only in 8-27% of the examinees.