Background: Brazilian gas station workers (GWS) are daily exposed to petroleum-derived hydrocarbons which are harmful. The aim of the study:The aim of this study was to evaluate the clinical complaints and the genotoxic effects in GWS. Materials and methods: Overall, 88 workers were recruited versus 127 controls. To test the influence of the time of exposure, we have divided the workers into two groups arbitrarily in: Group 1 (G1), with the short time of exposure, ≤ 3 years; and Group 2 (G2), with the longer time of exposure, > 3 years. Results: The most relevant complaints were headache (32%) and fatigue (20%), lipothymia (11%), and less commonly sleeplessness and crustiness (both 5%), drowsiness (4%), irritability (3%) and pruritus (1%). 12% of them reported having alcoholic histories. The workers presented concerning alterations found in the blood. Polycythemia (5/88), leukocytosis (10/88) and anemia (19/88) were the most frequent. Hepatic enzymatic damage showed an increase in LDH, bilirubin and AST. Anemia was not associated with the higher LDH rate. Micronucleus (MN) and comet tests were determined in erythrocytes and leukocytes, respectively. The MN test was significant for the total workers group (P = 0.034). As for the class of the comet tails, they were significantly higher for G1 (P = 0.001) and for the total of workers (P = 0.001), for the G2 the significance was borderline (P = 0.05). Conclusion: There were important clinical and laboratorial complaints. Genotoxicity assays indicated DNA damage and they can be useful to prevent serious diseases in this group.