Blood pressure declines in virtually all patients with severe congestive heart failure given an angiotensin-converting enzyme (ACE) inhibitor, but hypotension is of concern only if symptomatic. Acute renal insufficiency induced by an ACE inhibitor is due to reduced renal perfusion pressure together with blockade of angiotensin II-induced constriction of the efferent arteriole. Risk factors (or markers) for renal failure include hyponatremia, hypotension, volume contraction. Hyponatremia is an index of increased hemodynamic impairment, marked activation of the renin-angiotensin-aldosterone axis, and poor prognosis. Preventive measures for both ACE inhibitor-associated hypotension and renal insufficiency include withholding diuretics for a few days, initiating therapy with very small doses of ACE inhibitors, and cautious dose titration. Therapy for both hypotension and renal insufficiency involves increasing dietary sodium intake and reducing the dosage of, or temporarily discontinuing, the diuretic. The ACE inhibitor may have to be given at reduced dosage or discontinued for a time. If discontinuation is deemed necessary, administration of these survival-prolonging medications should be reinitiated after a brief respite whenever possible.