Factors of the immune system, including secreted pro-inflammatory interleukins, enable tumor control. However, against the background of prolonged chronic inflammation, they can trigger oncogenesis. Polymorphic variants in the coding and regulatory regions of cytokine genes can affect gene expression, mRNA stability, structure and activity of the protein product, with consequences on the levels of cells and body as a whole. This study aimed to search for the relation between polymorphic variants of interleukin genes IL1b (rs1143634), IL2 (rs2069762), IL4 (rs2070874), IL6 (rs1800795), IL8 (rs4073), IL10 (rs1800871) and risk of cancer, and to analyze the effect of polymorphic loci on concentration of serum interleukins. The study involved 585 persons chronically exposed to radiation. We established association of polymorphic IL4 site (rs2070874) with concentration of serum IL4 in individuals with chronic low dose-rate exposure of the red bone marrow 1.17 to 3507 mGy (mean value — 566 mGy). The content of serum IL4 in people with C/T and T/T genotypes (as per the dominant model) was significantly lower than in those with C/C genotype (p = 0.02). Polymorphic sites rs1143634, rs2069762, rs2070874, rs1800795, rs4073, rs1800871 were not found to be associated with the risk of malignant neoplasms in exposed individuals.