Effects of ethylene, gibberellins, and kinetin on the germination of two lots of Chenopodium album L. seeds, collected from the field in 1982 and 1983, were studied in relation to the availability of nitrate. The experiments were conducted in darkness and at temperatures ranging from 12 to 32 degrees C. Ethylene induced over 75% germination in the 1983 seed but had little effect on the 1982 seed. Nitrate was only slightly promotive in either of the two seed lots. A combination of ethylene and nitrate, however, acted synergistically on 1982 seed, resulting in as much germination as that induced in 1983 seed by ethylene alone. In 1983 seed, a combination of ethylene and nitrate was only marginally more effective than ethylene. A similar relationship was observed in the effects of gibberellic acid(4+7) (GA(4+7)) and nitrate on seeds from the two lots. The 1982 seed, which responded synergistically to combinations of nitrate with ethylene or GA(4+7) was found to contain an extremely low endogenous level of nitrate as compared to 1983 seed. Thus, high levels of either endogenous or applied nitrate appeared to enhance the germination response to ethylene or GA(4+7).Kinetin had no effect on 1982 seed and only a small promotive effect on 1983 seed. There was no synergism between kinetin and nitrate in either of the seed lots.