The anesthetic effects by dosages of Tiletamlne-Zolazepam in the dogs were investigated and then the optimal dosages for the operation of patients were suggested. 1. In groups of T+Z 20, 10 and 5 mg/kg administration, anesthetic periods are 180~300, 33~47 and 40~50 minutes, respectively and complete recovery from anesthesia was shorted with taking 53~72 minutes in the group of 5 mg/kg administration. 2. Reflex responses to eyelids, cornea and pharyngolarynx were maintained but pedal reflexes became considerably sluggish 3. It showed tachycardias on ECG but there were no specific dysrhythmias. On EEG, it showed low voltage-fast waves before anesthesia, high voltage-fast waves in induction stage, low voltage-slow waves in anesthetic stage and high voltage-fast waves again in recovery stage. 4. Surgical procedures could be performed satisfactorily in 6 cases of the 10 mg/kg administration group, but in 3 of 5 cases of 5 mg/kg administration group it could be completed after additional administration. 5. In conclusion, it was considered desirable for anesthetizing dogs that for healthy cases T+Z at the level of 10 mg/kg B.W. was administered, and for poor risk patients, 5 mg/kg B.W., followed by an additional administration in unsatisfied cases.