Glutathione S-transferases (GSTs) are principally involved in detoxification. These enzymes can be induced by an increased flux of substrate, such as occurs during pro-oxidative stress or antioxidant deficiency. We tested the hypothesis that the postulated oxidative stress in severe malnutrition would result in induction of GSTs in erythrocytes. Erythrocyte GST activity towards 1-chloro-2,4-dinitrobenzene (CDNB) was measured in 271 malnourished children (22 undernourished; 92 marasmic; 82 kwashiorkor; 75 marasmic-kwashiorkor) and 48 healthy children. GST activity in the malnourished children was significantly higher than the control group (P < 0.01). The GST activity in the four classes of malnutrition did not differ. There was a weak relationship between GST activity and the height deficit, but not with the weight deficit, or the clinical features displayed by the children. The 11 children that died had a higher value than the survivors. There was no change in GST with anthropometric recovery. We conclude that erythrocyte GST has been induced in children with malnutrition. Induction of erythrocyte GST may be the result of exposure of the children to oxidative stress during the months prior to their presentation with severe malnutrition.