Interactive Digital Television (iDT) is considered as the convergence of television and computer technologies. Usability evaluation for applications based on emerging information technology brings new challenges. The main iDT feature is that the user may interact with the application; therefore usability should be a main concern when designing iDT applications. Current research usually focuses on iDT applications from a technical point of view, rather than a user-centered approach. There is a need for new usability evaluation methods or at least for the use of traditional evaluations in novel ways. A set of specific usability heuristics was defined and validated, in order to help the usability evaluations of iDT applications. A usability checklist to be used when applying iDT heuristics is also proposed.