This paper describes an extensive research project concerning the leakage and influx of viewers during commercial breaks. The goal of this research project is to determine which factors bring about this kind of channel switching. The study covers the people meter data of 9 commercial breaks broadcast on the five main television channels in the Netherlands from January to April 1995. Of each of these commercial breaks, both the influx and the leakage of viewers were quantified. By means of multivariate analysis these two factors are related to a large set of explanatory variables, such as characteristics of: the break itself, the commercials in it, the audience, and the programmes before and after the break.