Emissions of nitrous oxide, methane, and carbon dioxide were measured at diverse locations in tropical forests of Brazil, Ecuador, and Puerto Rico, using a static open chamber technique. Mean fluxes to the atmosphere were 1.7¿1010, -0.7¿1010, and 1.5¿1014 molecules cm-2 s-1 for N2O, CH4, and CO2, respectively. The data indicate that tropical forests contribute a significant fraction of the global source for atmospheric N2O, about 40% of the current source and possibly 75% of the preindustrial source. Methane is consumed by soils on average, but the sink is an insignificant part (<5%) of the atmospheric cycle for the gas. Emissions of CO2 from forest soils are higher at equatorial sites than at middle or high latitudes, as expected from ecological considerations. Soils emit CO2 at rates more than twice as large as the rate of carbon infall in litter; hence much of the emitted CO2 must arise from root metabolism.