Blood, liver and kidney selenium levels were studied in male rats fed a Torula yeast diet with variations in selenium, vitamin E, and protein content. Kidney selenium levels were the highest of all tissues studied; liver levels were intermediate; and blood levels were lowest. A profound drop in the selenium levels of these tissues was observed in animals fed low selenium diets. Variations in dietary protein and vitamin E content did not affect selenium levels. Vitamin E administration prevented liver necrosis in animals receiving no supplementary selenium but had essentially no effect on their selenium levels. Blood and liver selenium levels were maintained at an almost constant level in animals receiving selenium regardless of whether it was supplied as 0.50 ppm or 0.25 ppm of the diet. Kidney selenium levels were maintained at the pre-experimental level when a diet containing 0.25 ppm Se was fed but rose sharply when 0.50 ppm was fed.