The cardiorespiratory effects of etomidate were measured in two groups of six patients with aortic or mitral valve disease. The induction of anaesthesia with etomidate 0.3 mg kg-1 was followed by a second dose 10 min later. After the first dose, a 19% decrease in systemic arterial pressure was associated with a decrease in systemic vascular resistance and left ventricular heart work. Cardiac index, pulmonary artery pressure and wedge pressure all decreased slightly. Central venous pressure and heart rate did not change. A slight increase in respiratory frequency failed to prevent an increase in PACO2. Changes after the second dose were similar. The two groups of patients did not differ significantly in their response to etomidate. No patient complained of pain during injection, nor did myoclonic movements occur.