The magnitude of termite methane (CH.sub.4) emissions is still an uncertain part of the global CH.sub.4 budget and current emission estimates are based on limited field studies. We present in situ CH.sub.4 emission measurements of termite mounds and termite mound subsamples performed in the Amazon rainforest. Emissions from five termite mounds of the species Neocapritermes brasiliensis were measured by use of a large flux chamber connected to a portable gas analyser measuring CH.sub.4 and CO.sub.2 . In addition, the emissions of mound subsamples were measured, after which the termites were counted so that a termite CH.sub.4 and CO.sub.2 emission factor could be determined. Mound emissions were found to range between 17.0 and 34.8 nmol mound.sup.-1 s.sup.-1 for CH.sub.4 and between 1.1 and 13.0 Âµmol mound.sup.-1 s.sup.-1 for CO.sub.2 . A termite emission factor of 0.35 Âµmol CH.sub.4 gtermite-1 h.sup.-1 was found, which is almost twice as high as the only other reported value for the Amazon. By combining mound emission measurements with the termite emission factor, colony sizes could be estimated, which were found to range between 55-125 thousand individuals. Estimates were similar to literature values, and we therefore propose that this method can be used as a quick non-intrusive method to estimate termite colony size in the field. The role of termites in the ecosystem's CH.sub.4 budget was evaluated by use of two approaches. Termite mound emission values were combined with local mound density numbers, leading to an estimate of 0.15-0.71 nmol CH.sub.4 m.sup.-2 s.sup.-1, on average, emitted by termite mounds. In addition, the termite CH.sub.4 emission factor from this study was combined with termite biomass numbers, resulting in an estimate of termite-emitted CH.sub.4 of â¼1.0 nmol m.sup.-2 s.sup.-1 . Considering the relatively low net CH.sub.4 emissions previously measured at this ecosystem, we expect that termites play an important role in the CH.sub.4 budget of this terra firme ecosystem.