As part of the comprehensive investigation of heat transfer in steam-boiler furnaces by the Special Research Committee on Furnace Performance Factors of the Society, the furnace heat-absorption efficiency and the distribution of heat absorption on the furnace walls were determined on boiler No. 1 at the Willow Island Station of the Monongahela Power Company, Willow Island, West Va. The unit is a single-drum boiler rated at 500,000 lb of steam per hr at 1350 psig and 950 F at the superheater outlet, with a water-cooled dry-bottom furnace that is fired through the roof with six multitip intertube burners. This paper presents the results of determination of furnace heat-absorption efficiency made by the Combustion Research Section of the Bureau of Mines, as part of the co-operative research program with the ASME Committee to study factors affecting furnace performance. The distribution of heat absorption in the furnace walls, investigated concurrently, is the subject of another paper, and together they comprise the third of a series of reports of investigations sponsored by the committee.