A theoretical model for bubble formation at a submerged orifice has been developed, which takes into account the interaction between the column wall and the growing bubble at the orifice, as well as the interaction between subsequent bubbles formed and detached from the orifice. Experiments involving high-speed photography and bubble frequency measurements were carried out with different chamber volumes, column and orifice diameters, and gas flow. In particular, it was found that decreasing the column diameter (that is, increasing the bubble-wall interaction) led to increased bubble-bubble interaction, as evidenced by a greater tendency for pairing and multiple bubbling. Simulated results using the theoretical model agreed very well with experimental data. (c) 2005 American Institute of Chemical Engineers AIChE J, 52: 86-98, 2006.