Significant variability of medical care exists in the United States that cannot be readily explained on the basis of severity of illness, patient demographics, or clinical necessity. One approach to promoting appropriate decision-making is to make the most recent and relevant information available to physicians in a practice guideline. Physicians are most likely to accept practice guidelines that address a specific need, are supported with scientific evidence, and offer the potential for improving patient outcomes. The implementation of a clinical practice guideline and its impact on the care of patients with uncontrolled hypertension are described.