Orthostatic hypotension developed in a 65-year-old man during treatment with quinidine and propranolol. Quinidine reduced standing blood pressure, attenuated the Valsalva response, and increased plasma norepinephrine concentrations, suggesting the presence of nonselective alpha-adrenergic blockade. The addition of propranolol inhibited the compensatory tachycardia and produced symptomatic orthostatic hypotension. Physicians should be alerted to the possibility of orthostatic hypotension when the alpha blocking effects of quinidine are combined with a beta blocking agent such as propranolol.