Occupational exposure to styrene was studied in a group of workers engaged in the production of fiberglass-reinforced plastics. Sister-chromatid exchanges (SCE), micronuclei (MN), and DNA damage (evaluated by means of comet assay) were measured in peripheral blood cells from the exposed workers and from a control population. Mandelic acid concentration, an indicator of styrene exposure level, was measured in urine samples collected at the end of the work shift. Average estimated values for styrene exposure were slightly below the threshold limit value (TLV) of 20 ppm recommended by the American Conference of Governmental Industrial Hygienists. Significant increases (P< or =0.01) have been found for SCE and MN frequencies and comet tail length among exposed individuals, as well as significant decreases (P< or =0.01) in the proliferation indices, as compared with control population. High correlation has been obtained between endpoints evaluated and exposure length, and increased values of SCE and MN frequencies and comet tail length have been found among smokers only in the exposed population. The high correlation obtained among SCE and MN frequencies and comet tail length, and the increase of these parameters in the exposed group with regard to control group justify the use of these three biomarkers in the evaluation of genotoxic effects in human populations exposed to styrene.