Benzene is a relatively common environmental and occupational contaminant with carcinogenic and clastogenic properties. Therefore, further understanding of the adverse effect of benzene is still a matter of interest. In the present study, induction of aberrations in the pericentromeric region of chromosome 1 (1q12) was examined by fluorescence in situ hybridisation (FISH) in both interphase and metaphase human lymphocytes after in vitro exposure to benzene at two concentrations (50 and 100 μmol/l). A weak but not significant increase of interphase cells micronuclei frequency was recorded at 100 μmol/l concentration in both donors examined (χ2 test, p > 0.05). No fluorescent signal indicating the presence of chromosome 1 was observed in adjacent micronuclei. In metaphase cells, hypoploidy (monosomy) and polyploidy (tetraploidy) were the types of numerical aberrations most often exhibiting classical satellite probe signal. Chromosome breakage in the investigated pericentromeric region was assumed in lymphocyte metaphase cultures of donor 2 exposed to a dose of 100 μmol/l.