Abstract: During anesthesia, monitoring of the patient using eyes, ears and fingers, with the aid of unsophisticated equipment is of fundmental importance. However, some non-invasire monitoring apparatus often gives definite help. We have used the following methods for monitoring with satisfactory results; 1. Monitoring of ventilation with Wright respirometer. Hypoventilation and postoperative residual respiratory depression by narcotics or relazants can thus be easily detected. 2. Monitoring the end tidal CO₂ concentration using infrared analyzer. A rough continuous estimation of alveolar CO₂ variation can be traced. Differential diagnosis of causative factors should only be made by good judgement. 3. Transcutaneous PO₂ monitoring. In interpreting the figures, the effect of blood pressure change must always be taken into consideration. In spite of many pitfalls, it is sensitive and useful for detection of hypoxia.