An increasing interest in intravenous anesthetic techniques has resulted from the availability of more efficacious intravenous agents, possible discomfor of the patient on endotracheal intubation and the concern over anesthetic pollution in the operating room. This study was done to investigate the effect of intravenous anesthesia with ketamine on the respiratory system by comparing arterial blood gas analysis before and after the procedure. Analysis of arterial blood for PCO2, PO2, pH, and excess were carried out. Heart rate and blood pressure were monitored on 15 patients in ASA class l for diagnostic or short procedures. Each patient was premedicated with atropine 0.01mg/kg and valium 0.2mg/kg intramuscularly 30 minutes before the procedure. ketamine was administered intravenously 1.0~1.5 mg/kg or intramuscularly 3~5mg/kg for induction of anesthesia. The anesthesia was maintained with ketamine 0.5~1.0mg/kg and valium 0.1mg/kg ever 5 to 10 minutes. The results of this study showed that ketmine anesthesia seemed not to cause any untoward effect on respiratory function. In other words, ketamine seems to be a safe and good intravenous anesthetic agent for diagnostic or short surgical procedures.