Considering the importance that the lexicon bears in the cognitive development of the human being, a piece of research was carried out to find out how much and which is the vocabulary that Chilean students of the last grade in Secondary School have so as to help in the school planning in this respect. This article presents the methodological steps followed in order to gather the corpus: the sample which has a national character and contains pioneering parameters in studies of this type, the questionnaire, the resulting statistics and the preliminary conclusions