Medication choices for the treatment of elevated blood pressure have a large potential impact on both patient outcomes and health care costs. Historic trends of prescribing for hypertension will advance the understanding of physician practice of evidence-based medicine. This study describes both long- and short-term trends in US antihypertensive prescribing from 1990 through 2004. Data were extracted from the National Disease and Therapeutic Index, a continuing survey of a national sample of US office-based physicians. Cox and Stuart and z tests were performed. Diuretics ranked among the top 3 antihypertensive drug classes throughout the entire study time span. Angiotensin-converting enzyme (ACE) inhibitors and calcium channel blockers (CCBs) were preferred over diuretics beginning in 1993, with diuretics surpassing CCBs in 2000. β-Blockers were consistently the fourth most common class until 2002, when exceeded by angiotensin II receptor antagonists (ARBs). Most recent trends indicated an immediate but short-lived increase in the prescription of thiazide diuretics after the new clinical evidence released in December 2002 demonstrating clinical equivalence of thiazides to ACE inhibitors and CCBs. In contrast, prescription of ACE inhibitors declined, accompanied by continuation of a pre-existing increase in the prescription of ARBs, whereas prescription of CCBs remained essentially stable after the new evidence was released. The recorded long- and short-term trends indicate that evidence-based clinical recommendations had an impact on antihypertensive prescribing practices, but the magnitude of impact may be smaller and of more limited duration than desired.