Historical aspects of the development and application of the vasodilator hydralazine are reviewed. The pharmacology, pharmacokinetics, metabolism, and mechanism of action are discussed, with emphasis on the parenteral use of this drug. It is reiterated that parenteral hydralazine is the preferred drug for the treatment of severe preeclampsia, but its usefulness in other forms of accelerated hypertension is also addressed. Through comparisons with other established antihypertensive agents, the efficacy and pharmacoeconomic potential of hydralazine are stressed.