Prazosin is an orally active post-synaptic selective alpha 1-adrenoreceptor antagonist that has been widely used in treating hypertension and congestive heart failure (CHF). Its role in the treatment of hypertension has previously been reviewed in this journal. Subsequent reports confirm its efficacy in treating mild to severe hypertension as a single agent or, more frequently, in combination with another antihypertensive agent and/or a diuretic. Recent studies of the metabolic effect of prazosin indicate that the drug may have a favourable effect on plasma lipids in hypertensive patients. Its recent use in treatment of congestive heart failure has shown prazosin to be comparable with nitroprusside in producing balanced arterial and venous dilation with generally sustained haemodynamic and clinical effects during long term therapy. Initial studies in Raynaud's phenomenon and in patients with aortic regurgitation or aortic stenosis or with mitral regurgitation are promising, but require confirmation from wider clinical experience. The drug has generally been well tolerated. The primary side effect of orthostatic hypotension can be largely avoided by beginning treatment with a low dose.