Termites are insects that are highly abundant in tropical ecosystems. It is known that termites emit CH₄, an important greenhouse gas, but their absolute emission remains uncertain. In the Amazon rainforest, we measured CH₄ emissions from termite nests and groups of termites. In addition, we tested a fast and non-destructive field method to estimate termite nest colony size. We found that termites play a significant role in an ecosystem's CH₄ budget and probably emit more than currently assumed.