Abstract: The incidence of hepatocellular cancer is one of the highest among the population in the tropics. This has been associated with the ingestion of foods contaminated by aflatoxin B1 (AFB1) a potent liver carcinogen elaborated as metabolite of Aspergillus fungi and some other fungi. Petrochemical refineries workers are in addition exposed to chemicals used in the refining of crude petroleum oil. Four petroleum-refining chemicals: N-methylpyrrolidone, Phenylenediamine, methylethylketone and Dialkylketonoxine, all obtained from a refinery situated in Nigeria were investigated in this study. Male Wistar albino rats, exposed subcutaneously to different amount of these chemicals and also orally given different concentrations of AFB1 in corn oil for 12 weeks, were observed to have higher levels of γ-glutamyl transferase enzyme activity in their livers and sera than the rats treated with either the chemicals or AFB1 only. They also have higher alkaline phosphatase (AP) activity in their sera. The activities of these enzymes were also higher than those observed in control rats treated with the carrier vehicle of corn oil only. Micronuclei and histopathology analysis results correlate with the results obtained in the enzyme assays. We therefore concluded that the petrochemicals are significant factor in hepatocellular cancer development in the refinery workers.