Fractional gas hold-up in air-water systems agitated by pitched four-blade upflow turbines was measured using the overflow method. The experiments were carried out in a 0.19 m i.d. vessel stirred by impellers having diameters of 0.31 D to 0.53 D. The blade width and the blade length were 0.25 d and 0.375 d respectively. Based on the experimental results, the gas hold-up was correlated as a function of the Reynolds and the Flow numbers. Attention must be given at the quality of the dispersion and the flooding for values of d/D < 0.42. In the state of flooding the proposed equation is not valid.