Experimental studies of gas hold-up in an mechanically agitated gas-liquid system of various physical properties of the continuous phase were carried out. The measurements were conducted in the slender agitated vessel equipped with baffles and single or double system of disc turbines. The results of the experiments were approximated by equations (19)-(26). The studies revealed that gas hold-up depends on the physical properties of the gas-liquid system and the number of the impellers on the common shaft.