Infrared emission from an active effusive volcanic eruption on Surtsey, Vestmannaeyjar, Iceland, was recorded by airborne and satellite infrared systems at irregular intervals between 19 August and 3 October 1966. Ground and lava temperature measurements and volumetric lava outflow data permitted a comparison to be made between total thermal-energy yield and radiant emission recorded by the satellite system. The Nimbus HRIR recorded radiant emission at a level of about 3% of the estimated total thermal yield.