Summary1. Male rabbits were starved in order to study the effect of a decrease in food intake on potassium metabolism. 2. Serial determinations of the exchangeable potassium content and urinary potassium and creatinine excretion were made in one group of animals. The mean decrease in exchangeable potassiumcontent was 29.8 and 54.6% of the baseline value after one and two weeks respectively. The corresponding mean decrease was 15.6 and 31.7% in body weight. No significant changes in urinary creatinine excretion occurred. 3. In a separate group of rabbits, tissue analyses for radiopotassium and water concentration after one week of starvation revealed no significant changes when compared with control animals, continued on a constant diet. 4. The decrease in total body potassium content, as measured by the exchange of isotopic potassium, as well as the loss in the urine during starvation could be accounted for on the basis of tissue catabolism without postulating an intracellular deficiency of this cation in...