Hemodynamic measurements, arterial and mixed venous blood gas tensions, and pH were determined in 12 adult cows (mean weight 538 kg) following the injection of 8 ml of 5% procaine between the first and the second lumber vertebra into the epidural space. Comparison of base-line data with obtained during unilateral segmented lumbar analgesia between T(13) and L(3) segments indicated significant decreases (P is less than 0.05) in total peripheral resistance and diastolic and mean arterial blood pressures, and significant increases (P is less than 0.05) in heart rate and cardiac output. Arterial and mixed venous blood gas tensions and pH, O(2)-uptake, stroke volume, left ventricular stroke work, left ventricular minute work and hematocrit did not change significantly (P is less than 0.05). Cardiovascular and respiratory values in two cows (mean weight 700 kg) given xylazine (50 mg, IM), were depressed from base-line data, but did not change significantly (P is less than 0.05) during unilateral segmental epidural analgesia of segments T(13 to L(3). The nonsedated healthy cow tolerates sympathetic vasomotor blockade between T(13) and L(3) segments well and is able to mobilize circulatory mechanisms effectively.