Cytogenetic tests - chromosome aberrations (CA), sister chromatid exchanges (SCE) and micronuclei (MN) - are most often applied in biomonitoring of the genotoxicity of potentially carcinogenic chemicals in human cells. One of the extensively studied genotoxins is diepoxybutane (DEB) - reactive biometabolite of butadiene (BD). Several studies showed a high SCE induction in human lymphocytes exposed in vitro to various concentrations of DEB. DEB also proved to be a potent inducer of chromosome aberrations and micronuclei. A bimodal distribution of SCE frequency after in vitro DEB treatment was observed. The aim of the present study was to examine the ability of DEB to induce different individual cytogenetic response measured by SCE and CA frequency. The possible influence of genetic polymorphism has also been taken into account, by including donors representing positive or null GSTM1 and GSTT1 genotypes. Our study supported the earlier results showing that DEB is an effective inducer of SCEs and CAs, causing also the decrease in replication index (RI). DEB bioactivity measured by SCE induction - but not by CA test - was significantly higher in GSTT1 negative than in GSTT1 positive donors. GSTM1 polymorphism had no influence on these endpoints. The donors GSTT1-/GSTM1+ were shown to be slightly more sensitive to DEB than GSTT1-/GSTM1- individuals. There was also observed a unimodal distribution of DEB-induced SCEs and CAs in the group, despite the fact that the experiment was performed on the lymphocytes obtained from both GSTT1 positive and negative donors.