Abstract: Apparatus (10) is provided for controlled delivery of gas to a patient. The apparatus is particularly useful for delivery of anaesthetic gases in circumstances where the patient is conscious and able to receive gas upon demand and also where ventilation is poor. The apparatus (10) includes an outlet duct (40) for conveying gas from a gas supply (25) to the patient. A waste gas inlet duct (60) is also provided for receiving gas exhaled by the patient. This is connectable to a suction source (at 35) for scavenging the waste gas. The waste gas inlet duct (60) is arranged so that it can receive gas exhaled by the patient with the outlet duct (via a valve or other diverting means (80)) and around the outlet duct (as guided by shroud (70)).