A method of aerating liquids, particularly for aerobic growing of microorganisms, has the steps of forming a circumferential stream of liquid, forming a longitudinal stream of liquid, and superimposing these streams so as to form a combined closed spiral-shaped stream. An arrangement is provided in which the circumferential stream is formed by an upright conduit tube and an impeller, the longitudinal stream is formed by a distributing element with a plurality of nozzles, and the superimposing of the streams is attained by fixedly mounting the distributing element relative to the impeller.