A combination of fentanyl-droperidol was administered intravenously alone or with atropine sulfate (2 doses--0.04 or 0.02 mg/kg of body weight) to determine if stable neuroleptanalgesia could be produced in the dog. Cardiovascular responses were recorded at 5, 15, and 30 minutes. Fentanyl-droperidol given alone caused a significant increase of peripheral resistance and mean arterial pressure at 5 minutes and then a decrease of these values over a postinjection period of 30 minutes. Left ventricular dP/dt increased significantly at postinjection minutes 15 and 30. In dogs given atropine concurrently with fentanyl-droperidol, there was significant increase in heart rate and decrease in stroke volume. Also, there were significant initial increases in diastolic and mean arterial blood pressures, ventricular contractility, and coronary blood flow. The dose of 0.02 mg of atropine/kg seemed optimal for intravenous administration with fentanyl-droperidol in the dog; when the atropine dose was 0.04 mg/kg, large inotropic and chronotropic effects were produced.