Seeds are the major propagules of plants, for which long-term storage requires maintenance of genetic integrity and physiological quality to assure seed viability. Generally, the seed quality declines during storage, but the physiological and biochemical mechanisms associated with reduced seeds quality and vigour are not well understood. Exposure of seeds to artificial aging was used in this study to understand natural seed deterioration for two oat (Avena sativa L.) cultivars (CDC Dancer and CDC Minstrel) and two barley (Hordeum vulgare L.) cultivars (CDC Copeland and CDC Kindersley). Accelerated aging was accomplished by exposing seeds to high temperature and high moisture conditions until seeds lost their viability. A significant (p ≤ 0.05) decrease in germination frequencies, viability, and vigour was noted for all genotypes during a five-day aging process. A faster and similar decline in seed quality was initially noted for the oat seeds as compared to the barley seeds. For barley, the initial seed deterioration was higher for CDC Kindersley as compared to CDC Copeland. A catalytic seed treatment (CAT™) on eight days aged seeds could partially reverse the effects of aging for all seed sources, except for CDC Kindersley. The SDS-PAGE gel profiles of major seed storage proteins did not reveal any noticeable changes during aging, whereas biochemical analyses showed increased DNA damage and various changes to seed carbohydrate composition during aging for all genotypes studied. A high raffinose to sucrose ratio in CDC Copeland barley seeds correlated with a significantly (p ≤ 0.05) lower decline in germination frequencies during the five day long aging process, but when aging was extended for another 10 days, a more rapid deterioration of the seeds occurred. Seeds of the oat cultivar CDC Minstrel, showing the smallest changes in carbohydrate metabolism during aging, exhibited the highest endurance to seed degeneration when aging was done for 15 days. Thus, seed deterioration progressed differently in the oat and barley genotypes and could not conclusively be correlated with differences in carbohydrate metabolism. Advisors/Committee Members: BAI, YUGUANG, CHIBBAR, RAVINDRA, MONICA, BAGA, KAREN, TANINO, CURTIS, POZNIAK, WANG, HONG.