Workers in the petroleum distribution trades experience relatively high-level exposures to fuel vapours whose consequences have not been fully elucidated. In this study, the possible relationship between occupational exposure to petroleum fuels and cytogenetic damages in peripheral lymphocytes was investigated. Twenty-three male, non-smoking workers from the area of Rome were enrolled in the study, together with age-paired controls with no occupational exposure to fuels. Peripheral lymphocyte cultures were set up for the analysis of structural chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and micronuclei (MN) in cytokinesis-blocked lymphocytes. Frequencies of CAs, SCEs and MN were compared between exposed and control groups, and evaluated in relation to blood lead level (as an indicator of engine exhausts exposure) for the whole group under study, and to yearly averaged exposure to benzene (8-h time weighted averages, as determined by repeated personal sampling) for fillingstation attendants only. Both CAs and SCEs were slightly increased in station attendants: 1.97 versus 1.46 aberrations per 100 cells, and 4.73 +/- 0.15 versus 4.48 +/- 0.11 SCEs/cell in exposed and control individuals, respectively. The difference between cumulative CA rates in the exposed and control populations was of borderline statistical significance (p = 0.066). However, when the exposed population was dichotomized for benzene exposure, a significant (p = 0.018) correlation of CAs with benzene exposure was found. The analysis of SCE data highlighted a significant increase of cells with more than 6 exchanges (HFCs), corresponding to the 75 degrees percentile of the overall distribution, in fillingstation attendants (relative risk (RR) = 1.3, 95% CI = 1.1-1.5) in comparison with controls. In the pooled population, the frequency of HFCs showed a statistically significant upward trend at increasing blood lead levels (chi 2 for trend = 27.8, p < 0.0001). A complex relationship between SCEs and benzene exposure was observed, with an increased frequency of HFCs in the medium exposure intensity class (RR = 1.5, 95% CI = 1.2-1.7), and no difference for exposure to higher benzene levels (RR = 1.0, 95% CI = 0.9-1.2), compared to reference subjects. Finally, the analysis of MN in both phytohemagglutinin- and pokeweed-stimulated cell cultures did not show significant excess of MN in binucleated lymphocytes of exposed workers with respect to the age-paired controls.