We studied cardiovascular effects of isoflurane in chickens during controlled ventilation. Following the determination of the minimal anesthetic concentration from the response to clamping of a digit, dose-related effect of isoflurane on heart rate and arterial pressure were studied. The minimal anesthetic concentration of isoflurane was 1.25 +/- 0.13% (mean +/- SD, n=9). There was a dose-dependent decrease in arterial pressure. The heart rate did not change significantly over a range of 1 to 2 times the minimal anesthetic concentration.