To invstigate the available dosage and effects of xylazine as preanesthetics on the propofol anesthesia in the dog, the experimental animals were randomly divided into 3 groups (xylazine 0.55 mg/kg (group 1), 1 mg/kg (group 2) and 2 mg/kg (group 3) were premedicated) and, monitored analgesic and anesthetic effect, body temperature, respiratory rate (breaths/minute), heart rate (beats/minutes). Also, hematological and serum chemical changes were monitored. In all experimental groups, the animals were recumbent just after propofol injection and time difference was not detected. Except vomitting after xylazine injection and insignificant ataxia during recovery, no significant side effects were observed. In group 2, loss of toe-web needle prick response time was slightly longer than group 1 but the response in group 2 and group 3 were similar, In group 2 and 3, the duration of anesthesia was longer than group 1 (2 folds) but there was no difference between group 2 and 3. Recovery time was prolonged in proportion to administration dosage of xylazine. In all experimental groups, the body temperature of animals was decresed gradually according to experimental time but no significant changes were monitored. The heart rate and respiratory rate were significantly (p<0.01, p<0.05) decreased after propofol injection Hematologically, no significant changes were monitored in total leukocye numbers, total erythrocye numbers, MCV, MCH, MCHC, serum GOT and GPT values Significant changes in all groups were not observed except significant increase in BUN, total-protein and abumin values of group 3. On the basis of these result, premedication of xylazine can be helpful in decresing some side effects and the dosage of propofol. 1 mg/kg of xylazine as preanesthetics on the propofol anesthesia in the dog is considered to be available.