Diffuse emission of CO2, CH4 and 3He was investigated in the summit crater of Teide volcano, Tenerife, Canary Islands. The results indicate that Teide volcano releases abundant CO2 not only from its active crater, but also from its flanks as diffuse soil emanations. The spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations. Our flux measurements indicate a total output of 380 ton⋅day-1 of CO2 and 1.6 ton⋅day-1 of CH4 by diffuse degassing. From the 3He/CO2 ratios and the CO2 flux we estimate a diffuse 3He flux of 0.052 mol⋅year-1. Isotopic analysis of carbon in soil gas samples from sites of high soil CO2 flux indicates a magmatic origin for the CO2, also reported by high 3He/4He ratios of 5.50 and 5.87 Ra. The origin of methane is more uncertain with low Δ13C values suggesting a biogenic contribution. ¿ 1998 American Geophysical Union