Vaporization of liquid mixtures is characterized by the decline of heat transfer, which depends on the mixture composition. As the total heat transfer is a function of the convective evaporation and the nucleate boiling mechanisms, the effect of liquid composition and the other variables of each mechanism have been analysed in this article. The analysis has been performed to identify the fundamental changes in nucleate flow boiling compared to nucleate pool boiling and boiling of the pure components. In the nucleate pool boiling region, the influence of mixture composition on the basic variables, i.e. bubble-departure diameter, frequency of departure and boiling site density, is presented. Models of the heat-transfer process which take mass transfer into account are compared with experimental data both of nucleate pool boiling and of nucleate flow boiling to predict the available data.