OBJECTIVE: To assess Canadian physicians' confidence in, attitudes about and preferences regarding clinical practice guidelines. DESIGN: Cross-sectional, self-administered mailed survey. PARTICIPANTS: Stratified random sample of 3000 Canadian physicians; 1878 (62.6%) responded. SETTING: Canada. OUTCOME MEASURES: Physicians' use of various information sources; familiarity with and confidence in guidelines; attitudes about guidelines and their effect on medical care; rating of importance of guidelines and other sources of information in clinical decision-making; rating of importance of various considerations in deciding whether to adopt a set of guidelines; and rating of usefulness of different formats for presenting guidelines. MAIN RESULTS: In all, 52% of the respondents reported using guidelines at least monthly, substantially less frequently than traditional information sources. Most of the respondents expressed confidence in guidelines issued by various physician organizations, but 51% to 77% were not confident in guidelines issued by federal or provincial health ministries or by health insurance plans. The respondents were generally positive about guidelines (e.g., over 50% strongly agreed that they are a convenient source of advice and good educational tools); however, 22% to 26% had concerns about loss of autonomy, the rigidity of guidelines and decreased satisfaction with medical practice. Endorsement by respected colleagues or major organizations was identified as very important by 78% and 62% of the respondents respectively in deciding whether to adopt a set of guidelines in their practice. User friendliness of the guidelines format was thought to be very important by 62%; short pamphlets, manuals summarizing a number of guidelines, journal articles and pocket cards summarizing guidelines were the preferred formats (identified as most useful by 50% to 62% of the respondents). CONCLUSIONS: Canadian physicians, although generally positive about guidelines and confident in those developed by clinicians, have not yet integrated the use of guidelines into their practices to a large extent. Our results suggest that respected organizations and opinion leaders should be involved in the development of guidelines and that the acceptability of any proposed format and medium for guidelines presentation should be pretested.