It is well known that some poisons, such as lead when stored in sufficient amount, may be mobilized from storage with the result that clinical illness appears or recurs. This phenomenon was first demonstrated experimentally for DDT by Fitzhugh and Nelson (1947). They showed that rats that had been fed diets containing DDT at concentrations of 600 parts per million (ppm) or more showed marked tremors when they were deprived of food completely. Rats deprived of all food after being fed 200 or 400 ppm showed increased irritability but no tremors. It has been assumed that these clinical effects resulted from a mobilization of DDT concurrent with the mobilization of body fat, but the effect of starvation on the concentration of DDT in various tissues and excreta has not previously been measured. This paper reports the results of such measurements in rats that were starved and in suitable controls. The results confirm that DDT is, in fact, mobilized into the circulation and into the brain during starvation and thus explain the clinical effects.