This paper describes the work carried out to select the most suitable set of Sublexical Units for Continuous Speech Recognition of Basque. Even if there are several dialects in Basque, only one of them has been used to choose the preliminary set of sounds. Bearing in mind this aim, a wide experimentation has been carried out to select Context Independent Phone-Like Units. Then, in order to obtain robust acoustic models for the language, the units have been evaluated with most of the dialectal variants of Basque. Finally, Decision-Trees based Context Dependent Sublexical Units are selected. For building the trees the classical methodology of Bahl and the efficient Growing and Pruning algorithm have been used.