The authors sought to explore the use and perceptions of clinical practice guidelines among internal medicine physicians. Through a Web-based survey, 201 board-certified internal medicine physicians rated their opinions on several statements using 7-point Likert scales. Most respondents (74.7%) felt that guidelines were suitable for at least half of their patients, although a failure to take comorbid conditions into account was a frequently cited barrier. For patients with cardiovascular disease, there was no difference between individual internists' perceptions of their own compliance with guidelines and their estimates of cardiologists' compliance (P = .14). A large majority of respondents (70.7%) believed that guideline committee member participation in industry-funded research introduces bias into guideline content (median [interquartile range], 5 [4-6]). Although most respondents felt that measuring physicians against guideline-based performance measures encourages evidence-based medicine (76.5%), opinions were split as to whether this practice distracts from patient care or compromises physician autonomy.