The evaluation of the usability of an interactive system is one of the most important steps in the user-centered design approach. Usability evaluation methods are quite diverse and many of them may be used to evaluate Interactive Digital Television (iTV) applications. Questions arise when deciding which method and/or combination of methods give more (relevant) information. Three iTV applications have been evaluated, applying several usability evaluation methods. Based on the effectiveness and efficiency of these methods, this paper proposes a methodology to evaluate the usability of iTV applications.