Bubble diameters were measured photographically in a bubble column, which was operating in the homogeneous regime with air and aqueous isopropanol solutions. The bubble size data were determined for several values of the superficial gas velocity, and used to fit bubble size distributions. The gas hold up was measured under the same conditions and its values were calculated from the bubble size distributions, using the theory for the conservation of the bubble size distribution function. The experimental results were compared to bubble size predictions given by models of bubble formation in orifices and to results from well-known correlations for the gas hold up. It has been verified that the models for bubble formation in orifices give reasonable predictions of the mean bubble diameter, while the correlations for gas hold up lead to poor agreement with the experimental data. The indirect measurement of gas hold up from the bubble size distribution was considerably more accurate.