The partition model of retention is developed for reversed phase liquid chromatography with multicomponent mobile phases. Simple equations for the retention and selectivity in ternary mobile phases are derived. For the systems in which the ratio of volume fractions of organic modifiers remains fixed, new linear dependences for retention factor and selectivity are proposed. These equations are successfully used to describe experimental data found in the literature. An influence of the nature of organic solvents and proportion in which they are mixed on retention and selectivity is discussed.