The aim of the present study was to advance the knowledge of the linguistic development of students with prelingual profound deafness, especially the acquisition and use of prepositions in Spanish, a lexical category with an important role in verbal comprehension. The researchers sought to learn the level of mastery students with prelingual profound deafness can achieve in the command of prepositions, depending on the system of communication they have been exposed to: classic oralism, Cued Speech, or signed language. The results show that the different systems of communication contribute, to different degrees, to the acquisition of Spanish prepositions, with the best results being obtained with Cued Speech. (Contains 3 tables, 3 figures, and 1 note.)