Petroleum products (PPs) consist of complex chemical mixtures, mainly hydrocarbons. Their composition varies considerably with source and use. Inappropriate manual handling and use of PPs, in countries like Nigeria, results in excessive skin contact with the possibility of hazard to health. There has been inadequate evidence to classify diesel, kerosene and hydraulic oil as human carcinogens and there is limited evidence for their toxicity and carcinogenicity in experimental animals. We compared the hepatotoxicity and clastogenicity of diesel, petrol or hydraulic oil with that of sodium arsenite (Na(2)AsO(2)) in mice. Our findings showed that these PPs are capable of inducing gamma-glutamyl transferase (gammaGT) activity in the serum and liver to levels comparable with that induced by Na(2)AsO(2). Mice treated with individual PPs have elevated mean liver and serum gammaGT at levels that are significantly different from the values observed for the negative control group. Also, the individual PPs alone have micronuclei formation induction activity similar to Na(2)AsO(2). We found that treatment with Aloe vera gel before the PPs significantly reduced mean liver and serum gammaGT, and the mean number of micronuclei scored when compared with groups administered each of the PPs alone, supporting the presence of hepatoprotective components in Aloe vera.