The poorest gains were made by pigs on the thiamine deficient ration. Likewise, the pigs on the thiamine deficient ration required much more feed per pound of gain, definitely showing that thiamine is concerned with the efficiency of feed utilization by the pig. Efficiency of utilization of the thiamine and riboflavin in the ration was much greater for pigs fed the natural grain rations than for those fed the purified rations. A positive relationship exists between thiamine intake and the deposition of this vitamin in the tissues of hogs. This makes it possible to increase the content of thiamine in pork by using feeds high in this vitamin. Usually the loin and ham are highest in thiamine content, followed by the other cuts in the following order: shoulder, heart, liver, and kidney. Pork liver is higher in riboflavin content than the other pork cuts, followed by the kidney, heart, ham, shoulder, and loin. A thiamine deficiency had no lowering effect on the deposition of riboflavin in the skeletal muscle tissues. There was a slight increased concentration of riboflavin in the liver and heart of the pigs on a thiamine deficient ration as compared to the pigs on a ration containing adequate thiamine. Symptoms observed on the thiamine deficient pigs were vomiting, anorexia, slight staggering, cyanosis, and a reduction in rectal temperature, heart beat and respiration during the final stages of the experiment. Enlarged hearts were obtained from the pigs on the thiamine deficient ration. Coliform counts of the feces of pigs fed the purified ration, with or without thiamine, were approximately 1000 times higher than for pigs fed natural grain rations. This may suggest a possible difference in intestinal vitamin synthesis between pigs fed natural grain rations as compared to purified rations. Further evidence for this possibility is presented and discussed. Data were obtained to show that storage of thiamine occurs and that the pig can utilize stored thiamine over a long period of time. Evidence for this is that 56 days were required for the pigs to lose their appetites after being placed on a thiamine deficient ration.