A study, presented here in two volumes and entirely in French, investigated the usefulness of introducing different varieties of Spanish in the classroom to improve listening comprehension skills, and the capacity of students to understand language variations. The experiment was conducted during two quarters at the University of Laval (Quebec), within four Spanish classes. The two experimental groups contained 17 and 21 students; control groups contained 16 and 22 students. Experimental groups were exposed to Spanish language varieties during classroom instruction, and the control groups were exposed to standard usage only. Results indicated definitively that the experimental groups showed broader comprehension skills, with attitudes toward Spanish language learning remaining positive. The first volume of the study describes the research methodology (hypothesis, theoretical framework, procedures, results, conclusions), and the second volume is devoted to the pedagogical material and measurement instruments used, and to the varied analyses performed on results. Contains an extensive bibliography. (MSE)