Few studies in the area of psychodietetics have concentrated upon the relationship between a single dietary nutrient and behavior. However, some vitamins have been shown to be particularly important to central nervous system activity. Among these is Vitamin C (ascorbic acid). Two experiments were done to determine the effects of ascorbic acid deficient diets on a learning task in which guinea pigs were subjects. Learning was defined as acquisition and extinction of shock-escape and shock-avoidance behavior. In Experiment I, twelve adult guinea pigs were fed diets containing two different deficient amounts of ascorbic acid for six weeks. They were then run on shock-escape, shock-avoidance and extinction schedules. No significant differences in behavior among the dietary groups were shown by statistical analysis, either in acquisition or extinction. In Experiment II, three adult guinea pigs were fed the same ascorbic acid-deficient diets as in Experiment I for six weeks after a baseline performance on a shuttlebox shock avoidance schedule was obtained. Performance after dietary treatment among or across subjects was not observably different from the performance prior to treatment. Serum and adrenal protein analysis confirmed that the dietary treatment had lowered the total ascorbic acid content of the serum and adrenals, but behavior did not show a corresponding or consistent change. These results indicate that ascorbic acid deficient diets fed to adult guinea pigs did not result in a change in behavior as observed on shock-escape, shock-avoidance, or extinction schedules.