A study is carried out to investigate the dynamic behavior of distillation columns with unequal molal overflow, both theoretically and experimentally. For the theoretical study, an approach is taken to transform the unequal molal overflow distillation system into a pseudo-equal molal one, which is then used to develop dynamic equations representing unequal molal overflow distillation columns. For the experimental study, the acetone-water binary system is chosen, and the transient response in temperature of a 11-plate bubble cap distillation column to step disturbances in the reflux rate is measured. Comparison of experimental results with theoretical predictions shows that the pseudo-equal molal overflow approach gives a reasonably satisfactory prediction, which is superior to that made by the dynamic equations based on the assumption of constant （or equal） molal overflow. The results of the present study therefore indicate the feasibility of extending the pseudo-equal molal overflow approach to multicomponent distillation systems.