In bioreactors, the purpose of aeration is to transfer oxygen from air bubbles into the liquid phase where the biological reactions occur. In some cases, aeration is also used as a mixing tool. In all aeration devices there is a continuous liquid phase and, generally, a dispersed gas phase in the form of bubbles. The most common aeration devices are stirred tank reactors, bubble columns and sieve plate reactor-towers. Bubble shape, bubble volume, and associated liquid flow patterns are key aspects of bubble dynamics in sieve plates. The most prevalent bubble shapes are spherical, oscillating (wobbling), ellipsoidal, spherical-cap, and skirted. Bubble volume and bubble shapes determine the surface to volume ratios, a very important parameter in determining overall mass transfer rates. Mass transfer in sieve plate reactors takes place, predominantly, within the oscillating bubble regime. Mass transfer rates from oscillating bubbles can be orders of magnitude larger than mass transfer rates from spherical bubbles. A fundamental correlation for mass transfer from single, oscillating bubbles was developed based on a solution of the mass transfer equations following the domain perturbation technique first outlined by Joseph (1973) and the hydrodynamics results of Tsamopoulos and Brown (1983) The correlation derived here entirely from hydrodynamics and mass transfer concepts, introduces the effect of interfacial tension in bubble mass transfer from fundamental concepts, has no adjustable parameters, and agrees very well with experimental data.