In an attempt to study the effect of vitamins on hypoxia, two experiments were carried out by using animal as follows: A) the survival rate and time in mice treated with nicotinamide alone or vitamin complex were investigated under the decompressed hypoxic condition simulated an altitute of 10, 500-11,000m. B) NAD+ in the heart and liver tissues as well as lac-tate, pyruvate and lactate/pyruvate (L/P) ratio in the brain of the rats given nicotinamide alone or vitamin complex were measured after asphyxic anoxia.By this study, the following results were obtained; 1) both nicotinamide and vitamin complex could prolong the survival time significantly (p