Phrase-based statistical translation systems are currently providing excellent results in real machine translation tasks. In phrase-based statistical translation systems, the basic translation units are word phrases. An important problem that is related to the estimation of phrase-based statistical models is the obtaining of word phrases from an aligned bilingual training corpus. In this work, we propose obtaining word phrases by means of a Stochastic Inversion Transduction Grammar. Preliminary experiments have been carried out on real tasks and promising results have been obtained.