A preliminary account of the 1953 expedition to Kilimanjaro, Tanganyika, by members of the Geology Department of the University of Sheffield and the Tanganyika Geological Survey. About 300 square miles above 9,500 feet were explored. The succession of lavas and the structure on each of the three main centers of volcanic activity that comprise the summit--Shira, Kibo, and Mawenzi--are discussed. While the age relationships of the lavas to each other have been established with greater certainty, the age of the mountain, from direct evidence, is unknown.