Some theories on interpreting tell us that interpreting is just understanding in one language and explaining in another; it is simply the transmission of the meaning as it has been intended by the original speaker. In order to achieve this objective, interpreting into the interpreter's mother tongue is essential, since that is where the interpreter possesses an underlying linguistic and cultural competence (théorie du sens). The author believes that this theoretical approach does not take into account either the implications that the languages involved and their direction have on the interpreting process, or the influence that direction has on the training strategies for the acquisition of the technique of simultaneous interpreting. In this paper the linguistic and cultural characteristics of the English and Spanish languages, as well as their implications for the training of future interpreters from English into Spanish, are analyzed. Finally the author presents a training proposal for the acquisition of SI technique targeted specifically at Spanish-speaking students.