The objective of the study reported was to investigate the hypothesis that a diet low in protein would affect ability to detoxify pesticides. If this were so, the results would have application to use of pesticides in areas of the world where the diet is normally low in protein. To test the hypothesis, weanling albino rats were fed for 4 weeks on three types of diet: (1) a standard laboratory chow diet, (2) a synthetic diet containing 8% casein but otherwise adequate in calories, vitamins and minerals, or (3) the same diet as group (2) but containing a normal protein content of 27% casein. DDT was selected as the challenging agent and was given orally at the end of 4 weeks in a range of doses which permitted delineation of the LD(50) and associated clinicopathological signs of toxicity in rats of the 3 dietary groups. The median lethal dose and the syndrome of toxicity were essentially similar in all three groups of rats. Within the parameters of toxicity measured, the results suggest that DDT toxicity is not augmented by a low-protein diet.