Present commercial systems for dry flue gas desulfurization use a slurry of hydrated lime sprayed into a chamber and contacted with the hot flue gas. Heat from the gas dries the droplets and yields a dry product containing calcium sulfite and calcium sulfate. However, sulfur dioxide (SO2) collection efficiency is low, energy and process costs are high, and the process still involves handling a slurry of lime. Dry absorbents for SO2 have been studied and, up to the present time, only sodium-based materials have been found to be sufficiently reactive. The expense of additional process equipment and environmental concerns over the disposal of soluble sodium sulfite and sodium sulfate waste have precluded their use. The availability of a highly reactive calcium oxide for dry SO2 absorption would offer substantial economic and environmental benefits. This paper discusses the development of such a highly reactive calcium-base absorbent. This highly reactive calcium oxide reacts in the dry state with sulfur dioxide and oxygen in the flue gas at high temperatures, in close to stoichiometric amounts, to yield a dry calcium sulfate product. Absorption tests were conducted using a differential packed-bed reactor in an electrically heated furnace. A simulated flue gas mixture containing 0.3% to 0.4% SO2 was reacted with the calcium oxide over a range of temperatures and reaction times. Initial reaction rates were determined, the reaction products were analyzed, and overall conversion calculated.