This article attempts to trace the origins of Mau Mau movement in Nakuru, the capital of the White Highlands, and to follow its development through the turbulent post-war years. Mau Mau here is seen as a distinct militant movement which advocated the use of violence in the anti-colonial struggle. It developed within the ranks of the Kikuyu Central Association whose moderate political strategy it rejected. It had a distinct social basis, both its leadership and its mass support coming from the ranks of the dispossessed urban Kikuyu lumpenproletariat. Mau Mau emerged, by 1952, as the dominant African political force at the cost of alienating most non-Kikuyu tribes, and intensifying divisions and hatreds within Kikuyu society. Although Mau Mau did not have definite plans for a large-scale guerrilla war when the State of Emergency was declared in October 1952, nor was it prepared for such a war, it was certainly developing along these lines. There was a large measure of continuity between pre-Emergency Mau Mau and the forces which were later engaged in the forest fighting. The forest fighting was primarily a response, not of the bewildered Kikuyu masses, but of an organized militant and violent movement. It is not suggested that Nakuru's model applies to other Kikuyu areas. On the contrary, it is suggested that the full story of Mau Mau in Kenya will be revealed only after a series of intensive local studies have been undertaken.