Mass transfer in typical areation devices such as sieve plate reactors and bubble columns takes place predominantly within the oscillating bubble regime. Mass-transfer rates from oscillating bubbles can be several times larger than mass-transfer rates from rigid bubbles. The hydrodynamics of oscillating bubbles has been described by Tsamopoulos and Brown (J. Fluid Mech. 1983, 127, 519-537) and later by Feng (SIAM J. Appl. Math. 1992, 52 (1), 1-14), using the domain perturbation technique first developed by Joseph (Arch. Ration. Mech. Anal. 1973, 51, 295-303). A high-speed video imaging system was used to determine the shapes of oscillating bubbles for a wide range of fluids and operating conditions. Air bubbles introduced through an orifice were recorded while rising inside a liquid. When the liquid was water, a hydrogen bubble technique was used to determine pathlines around the rising bubble. The experimental data on shapes and pathlines were compared with bubble shapes and pathlines created using theoretical models.