Glutathione levels were found to be decreased while lipid peroxide levels were increased in total liver homogenates 6 h following paracetamol treatment (500 mg kg−1 i.p.). Furthermore, it has been determined that cytosolic glutathione S-transferase (GST) activity was decreased and glutathione peroxidase (GSH-Px) activity remained unchanged. On the other hand, a decrease in liver microsomal lipid peroxide levels and an increase in GST and GSH-Px activity has been observed. We concluded that decreased lipid peroxide levels in microsomes could be a consequence of increased GSH-Px and GST enzyme activities. In this way, these glutathione-related defence enzyme systems may play an important role in protecting microsomes from lipid peroxidation.