Newborn rats and young guinea pigs have been exposed to high oxygen concentrations with subsequent analyses of ascorbic acid in liver and brain tissue. Newborn vats show a depletion of liver ascorbic acid only after exposure to 100% oxygen. Extending the exposure period in 70% oxygen did not result in any depletion. Brain ascorbic acid levels in newborn rats were depleted by exposure to both 100% and 70% oxygen until the 14th day of life. After that age, exposure failed to cause depletion. Guinea pigs identically exposed showed ascorbic acid depletion in both brain and liver tissue with the more marked depletion occurring in liver tissue. Abnormalities in the eyes of the experimental guinea pigs were demonstrated. Results of the tissue Vitamin A analyses are incomplete and inconclusive at this time. / Master of Science