Abstract: A device for the transfer of one or more substances between a gas and a liquid, the gas being introduced into the liquid in the form of bubbles from which the said substances are transferred to the liquid whereupon the excess gas is removed together with any substances transferred from the liquid to the gas. Characteristic for the device is a narrow annular gap (10), arranged vertically, for the liquid, a gas inlet (20), arranged in close connection to this gap (10), this gas inlet being adapted so that it introduces the gas uniformly distributed along the whole periphery of the gap (10), and means (34,36) for the removal of the excess gas.The device is intended in particular to be used as a so-called oxygenator when the said liquid is blood and the said gas is oxygen or an oxygen mixture. Carbon dioxide from the blood will then be removed together with the excess gas.