The limitations of present postoperative analgesic methods are outlined and the rationale of nitrous oxide-oxygen analgesia is developed by contrast. Concentrations of 30–70 per cent nitrous oxide in oxygen were used, being delivered from a standard anaesthetic machine through facepiece or nasal catheter. The application of the technique in 103 postoperative cases, 82 of which had had thoracic surgery, is discussed. Two illustrative cases are described in detail. The analgesia was excellent and a clear improvement in respiratory exchange, acid-base balance and oxygenation was demonstrated. Other uses described are the management of the agonizing pain of acute coronary insufficiency and of acute aMominal pain pending diagnosis. A final suggestion concerns the use of the method in painful terminal states.