Requirement for endogenous ethylene in the germination of two lots of Chenopodium album L. seeds, with different inherent degrees of dormancy, was studied. The seeds produced ethylene upon imbibition, and an increase in ethylene emanation either preceded or coincided with the earliest occurrence of radicle emergence. The amounts of ethylene produced were directly proportional to the final germination percentage achieved, regardless of the seed lot or conditions of germination. Breakage of dormancy by a combined treatment with GA4+7, NaNO3 and white light (stimulated seeds) substantially increased ethylene production and germination. Although an application of 2-aminoethoxyvinyl glycine strongly suppressed ethylene production, it had no effect on the germination of non-dormant or stimulated dormant seeds. Application of 2,5-norbornadiene to antagonize ethylene action did not inhibit germination of non-dormant seeds. However, norbornadiene strongly inhibited the germination of stimulated dormant seeds, and this inhibition was overcome by the application of exogenous ethylene. It is concluded that, in order to germinate, non-dormant seeds do not require the ethylene they produce. However, induction of germination in dormant seeds depends on the action of ethylene produced during this process. The passage from dormancy to germination may, therefore, involve two steps: an ethylene-requiring transition to non-dormant state, followed by the germination itself that does not depend on ethylene.