Canadian clinical practice guidelines are being developed for radiological services. In the first part of a two-part article outlining the history and process of this guidelines development, the author discusses several national and provincial initiatives in this area. A National Partnership for Quality in Health, involving many major physician organizations, was formed in 1990 to promote clinical practice guidelines in Canada. The Canadian Association of Radiologists (CAR) participated in its workshops. CAR decided in 1994 to ask its Task Force on Standards to assume the task of development of appropriateness guidelines in diagnostic imaging. After review of British and US guidelines in radiology, the Task Force decided to develop guidelines tailored to the practice in Canada through interdisciplinary consensus. The CAR subsequently entered into an agreement with the Health Services Research in Radiology Initiative of McMaster University, Hamilton, Ont., to investigate guidelines development, and decided to avoid taking "ownership" of guidelines. Guidelines development is based on the Guidelines Development Cycle of Browman and associates and is condition-based, rather than being all-encompassing or equipment-based. Guidelines developed to date or in progress include those for chest radiography in asymptomatic populations (such as routine health examinations or screening of smokers), for radiographs of foot and ankle injuries, for diagnosis of deep-vein thrombosis and for ultrasonography in normal pregnancies.