Rapid lowering of blood pressure can precipitate or worsen ischemic strokes. This usually has been observed in the setting of profoundly lowered pressure and hypotension. We report on six patients in whom ischemic neurologic injury ensued or worsened after moderate reduction of blood pressure by pharmacological treatment. The 6 patients suffered new or worsened ischemic neurologic deficits after receiving oral or intravenous antihypertensive medications, mostly after relatively small doses. Mean arterial blood pressure in these patients was decreased by 25 +/- 7.7%, or 37 +/- 16 mm Hg (mean +/- SD) without resultant hypotension. These cases emphasize the potential hazards of moderate blood pressure reduction by antihypertensive medications in the setting of an acute ischemic stroke or transient ischemic attack (TIA), as well as rapidly treated hypertension even in those who have not yet manifested ischemic symptoms.