When seeds of soybeans (Glycine max Amsoy var.) or safflower were stored under high O(2) concentrations, their per cent germination declined rapidly. For example, soybean seeds stored under 7.7 atmospheres O(2) pressure at 25 degrees C and 17% moisture lost all viability within 22 days, whereas under 7.7 atmospheres N(2), the per cent germination remained greater than 80%. Germination decreased continually in O(2) pressures ranging from 0 to 7.7 atmospheres. High levels of O(2), moisture, or temperature each acted independently to cause losses of germination, but when applied simultaneously, these factors acted synergistically. Soybean seeds were also aged under conditions of high temperature (44 degrees C) and humidity (100% RH), which have been routinely used to accelerate aging. Under these conditions, no O(2) dependence of seed death was observable.Increased lipid oxidation was not detected in seeds that had lost germination ability due to high O(2) treatment. Seeds of two safflower varieties that contained either high oleic or high linoleic fatty acid compositions were subjected to high O(2) treatment. Although the lipid of the high oleic variety is markedly more stable to oxidative degradation, we detected no significant difference in the O(2) tolerance of these seeds.