The emission of hydrogen sulfide from Amazonian floodplain lakes was detected mainly during the period of falling water of the Amazon river, which peaks out in September and October. Hydrogen sulfide was present even in some surface water samples (up to 0.40 mg at. H2S-S/1). A part of the emitted hydrogen sulfide is recycled on a regional or local scale by means of biospheric trap mechanisms and eventual rainout, sustaining the tight sulfur cycle of the Amazonian tropics. But a certain amount of the emitted hydrogen sulfide contributes to the atmospheric sulfur budget. Under cold front conditions, however, the emitted hydrogen sulfide is rapidly recycled into the tropical forest stands.