Anesthetic agents are useful in inducing the anesthesia for surgical operations and various biological experiments, but they can disturb the body homeostasis and cause the stress in animal. Much efforts have been directed on reducing such side effects of anesthesia. In this work, we measured the serum ACTH, corticosterone and glucose concentration in rabbits to compare the degree of stress induced by two commonly-used anesthetics, ketamine, xylazine, and the combination of xylazine and ketamine. 1. The anesthesia was induced in about 10 min in the rabbits treated with xyalzine, ketamine and xylazine-ketamine. The duraion of complete loss of righting reflex were 12, 13 and 115 min in the groups treated with xylazine, ketamine and xylazine-ketamine, respectively. 2. Serum ACTH concentrations in all treatment groups were gihger than those in control group. At 30 min after the administration of the drugs, serum ACTH levels in ketamine-treated group were significantly higher than those in control, xylazine- and xylazine-ketamine-treated groups. However, at 1, 2, 5 and 9 hours after the drug administration, serum ACTH levels in xylazine-treated-group were gihger than those in control. 3. Serum corticosterone levels in xylazine- and xylazine-ketamine-treated groups were lower than those in control or ketamine=treated groups at 0.5 and 1 hour after the administration. However, at 5 and 9 hours after the administration, serum corticosterone levels inxylazine- and xylazine-ketamine-treated groups were significantly higher than those in ketamine-treated group or control. 4. Serum glucose levels transiently increased to 3 tives of the pre-injection levels at 0.5 and 1 hours after the administration in xylazine or xylazine-ketamine-treated groups, but were not changed in control and ketamine-treated group. These results indicate that xylazine-induced stress lasts longer than ketamine-induced, suggesting that the difference in stress-related hormone levels during anethesia could be due to the differences in modes of actions of individual drugs used and the depth of anesthesia.