Termites may emit large quantities of methane, carbon dioxide, and molecular hydrogen into the atmosphere. Global annual emissions calculated from laboratory measurements could reach 1.5 x 1014 grams of methane and 5 x 1016 grams of carbon dioxide. As much as 2 x 1014 grams of molecular hydrogen may also be produced. Field measurements of methane emissions from two termite nests in Guatemala corroborated the laboratory results. The largest emissions should occur in tropical areas disturbed by human activities.