Abstract: Blood and gas transfer apparatus comprises a substantially rigid receptacle; a collapsible bag in the receptacle, there being space formed between the bag and receptacle; structure in the receptacle forming first porting communicating with the bag and via which blood may be transferred into and out of the bag, and second porting communicating with that space between the bag and receptacle for selectively transferring gas into and out of the space; whereby in a first mode of operation blood may be drained into the bag via the first porting, and gas may be removed from the space via the second porting, and in a second mode of operation, blood may be drained from the bag via the first porting, and gas may be introduced into the space via the second porting, the structure including neck means on the receptacle and a cap received on the neck and forming the first and second porting.