Magnesium deficiency as well as excess sucrose in the diet have been shown to be associated with the generation of reactive oxygen species (ROS).In the present study we have investigated the combined effect of low magnesium high sucrose diet on the development of oxidative stress in rats.Male Wistar rats were divided into four groups and fed control (C), low magnesium (LM), high sucrose (HS) and low magnesium high sucrose (HSLM) diet for a period of 3 months. Levels of various antioxidants, viz. ascorbic acid, vitamin E, uric acid, glutathione and non-protein thiols were determined along with malondialdehyde levels (lipid peroxidation marker). Anti-oxidant enzyme activities were determined in livers of experimental diet fed animals.Compared to controls, significantly increased lipid peroxidation was observed in plasma and liver tissue of animals in the three experimental groups, however, the combined HSLM group showed greater lipid peroxidation. Levels of various antioxidants fell significantly in plasma and tissue of LM, HS and HSLM rats. Total thiols as well as liver non-protein thiols followed a similar trend with the greatest drop in anti-oxidant potential seen in the HSLM rats. The activities of the anti-oxidant enzymes viz. SOD, GST and catalase also declined considerably in test animals w.r.t controls, with the HSLM group showing the lowest activities.These findings suggest that a diet low in magnesium and high in sucrose causes oxidative stress in rats, as reflected by increased lipid peroxidation and reduced anti-oxidant potential.