For many years, the term "Ulsterization" has been the cynical term used to describe the British Government's transfer of the responsibility for law enforcement to the local population of Northern Ireland. For more than 25 years, students of the Northern Ireland conflict have believed there was a radical change in British security policy during the mid-1970's. It has been argued that the British Government had become tired of the conflict and essentially withdrew from investing its resources in Northern Ireland's security by transferring the responsibility (including the human cost) for law enforcement to the local population. Given that the two local security agencies, the Royal Ulster Constabulary (RUC) and the Ulster Defence Regiment (UDR) were predominantly Protestant in composition, "Ulsterization" has been viewed by members of the Catholic community as a cynical move designed to give Protestants control of events in Northern Ireland. Using quantitative as well as qualitative evidence, this study argues that the concept of "Ulsterization" has been misunderstood, even to the extent that it is a totally false description for the policy changes of 1974-75. The article first shows that the concept of "Ulsterization" had been a well-established theme of the British Government's thinking about Northern Ireland long before the Labour Government came to power in 1974. Next, the article critically evaluated the Government's motives for the policy changes of 1974-75. The core of the article, however, concerns the concept of "professionalization," which the author believes is a much better conceptualization of the policy changes of 1974-75 than the notion of "Ulsterization." In substantiating his argument, the author presents a detailed discussion of the quantitative evidence advanced by Brendan O'Leary and John McGarry in challenging the claims of the Irish Government in its persistent lobbying of the British Government to abandon the policy of so-called "Ulsterization" and its implications. In addition to arguing for use of the term "professionalization" in efforts to upgrade the performance of local police forces, the author also argues for the use of the term "de-militarization" to explain the process of increasing the role of the RUC in law enforcement. It was the intent of the British Government to move toward nonsectarian law enforcement by recruiting local residents and training new and existing law enforcement personnel to provide professional and unbiased police performance. The policy mistakenly labeled with the derogatory term of "Ulsterization" was in fact a reduction of the Army's overt military posture in Northern Ireland in an effort to supplant it with an increased emphasis on the professionalization of local, native policing. 4 figures and 50 notes