We studied the relationship between DNA damage, DNA repair rates and messenger RNA (mRNA) expression levels of cell cycle genes TP53, p21(CDKN1A), BCL2 and BAX in a group of 71 styrene-exposed workers and 51 control individuals. The exposure was assessed by measuring the concentration of styrene at workplace and in blood. Parameters of DNA damage [measured as single-strand breaks (SSBs) and endonuclease III-sensitive sites], γ-irradiation-specific DNA repair rates and mRNA levels of studied genes were analyzed in peripheral blood lymphocytes. The workers were divided into low (<50 mg/m³) and high (>50 mg/m³) styrene exposure groups. We found negative correlations between mRNA expression of TP53, BCL2, BAX and styrene exposure (P < 0.001 for all parameters). In contrast, p21(CDKN1A) mRNA expression significantly increased with increasing styrene exposure (P = 0.001). SSBs and endonuclease III-sensitive sites increased with increasing mRNA levels of TP53 (P < 0.001 for both) and BCL2 (P = 0.038, P = 0.002, respectively), whereas the same parameters decreased with increasing mRNA levels of p21(CDKN1A) (P < 0.001, P = 0.007, respectively). γ-Irradiation-specific DNA repair rates increased with p21(CDKN1A) mRNA levels up to the low exposure level (P = 0.044). Our study suggests a possible relationship between styrene exposure, DNA damage and transcript levels of key cell cycle genes.