Guidelines for the pharmacologic and nonpharmacologic management of hypertension were first published in the 1970s and subsequently revised in the 1980s and 1990s. In this review, we focus on guideline modifications of the past 20 years and describe the main similarities and differences between the guidelines recently published by the World Health Organization/International Society of Hypertension committees and the US Joint National Committee. These guidelines agree on fundamental issues such as the careful assessment of patients' overall risk and target-organ damage, the treatment of elderly hypertensive individuals and isolated systolic hypertension, and the importance of persistent blood pressure reduction below 140/90 mm Hg. The committees also disagree in a few areas, such as the class of drugs to be used as first-line treatment and the use of ambulatory blood pressure monitoring. These disagreements reflect the limited scientific evidence on these specific topics.