The production of ethanol under anaerobic and aerobic conditions is suggested as a sensitive indicator of seed aging. Seeds of sweet corn (Zea mays L. `Jubilee') and lettuce (Lactuca sativa L. `Salinas') were aged at 75% relative humidity and 45C to obtain five aged seed lots and compared to a nonaged control sample. The percent germination decreased while percent abnormal seedlings initially increased with seed aging. Anaerobic treatments were induced either by immersing seeds in distilled water for sweet corn or in a solution of 50 mM glucose and 5 mM KPO4 buffer adjusted to pH 5.6 for lettuce. Aerobic treatments were performed by placing seeds in a plastic chamber filled with a known amount of glass beads sufficiently moistened to allow imbibition. Ethanol was measured after 12 and 24 hours from lettuce and sweet corn, respectively. Aqueous extracts were analyzed by immobilized enzyme technology and verified by gas chromatography. Anaerobiosis induced large amounts of ethanol production compared to aerobic treatments. The amount of ethanol decreased with seed aging duration under anaerobic conditions while these trends were generally reversed under aerobic conditions. The ratio of ethanol produced under anaerobic compared to aerobic conditions was best able to separate differences in seed quality due to aging.