There are an increasingly greater number of authors who support the use of qualitative methodology in their research (Glaser & Strauss, 1967: Geotz & Lecompte, 1980; Bogdan & Bliken, 1982; Firestone & Herriot, 1983; Howe, 1985; Filstead, 1986, etc.). However, there are problems offering a clear conceptualization of the above mentioned notion owing to the fact that often qualitative (Q) and quantitative (C) terms are used without specifying their concrete meaning, or are even referred to polysemically. Furthermore, authors even differ in the identification of the different uses of the terms in question. With the aim of solving these problems, we thought it suitable to carry out an exploratory content analysis of the characteristics given by authors to the terms C and Q. The results illustrate that Reichardt and Cook's proposal (1986), although representing a significant advance in the field, does not go far enough, given that it does not gather all the possible uses that authors attribute to the terms C and Q. This may, in our opinion, be considered as proof of the need to search for new criteria and/or reformulate the already existing ones.