In multiphase flow reaction systems, in general, an extrapolation of small diameter behavior to larger ones is always an important and challenging task. The critical issue in such an extrapolation remains to be mixing and hydrodynamic characteristics. It needs reliable similarity criteria that would result in similar mixing and hydrodynamics and hence transport and performance in two different scales. Numerous experimental and computational studies have been performed to investigate the flow behavior of bubble column reactors for a proper design and scale-up. Experimental techniques vary from simple visual observation to more advanced noninvasive diagnostic techniques. On computational front the progress has been made from simple reactor models to fundamentally based Computational Fluid Dynamics (CFD). Such studies ultimately provide a knowledge that help in understanding the hydrodynamic and mixing characteristics of these reactors and would aid in its scale-up. Based on these studies, various methodologies have been proposed in literature for scale-up and/or to maintain their hydrodynamic and mixing similarity. This article attempts to review the current state of reported dynamic similarity and scale-up methods of bubble column reactors. It mostly covers the methods reported in open literature. The scale-up practices in industry appear to be proprietary for obvious reasons.