The accuracy of CFD calculations of bubble column reactors is often limited by a lack of knowledge regarding bubble coalescence and break-up rates. The models describing coalescence and break-up rates have parameters, which cannot be estimated from the available physical properties. The main objective of this work was to test different coalescence and break-up models and to develop experimental methods for estimating the model parameters. In the experiments bubble size distributions were measured photographically at-several reactor heights. A population balance model describing the evolution of the bubble size distribution with respect to reactor height was developed and solved numerically.