The aim of this paper consists in offering a critical perspective on the main procedures for the objective selection of lexical contents in second language teaching. Three criteria are considered: frequency, use and availability. After analysing the methodological bases on this research field, and its results in the study of Spanish vocabulary, it is found out that none of them is satisfactory enough. The frequency criterion is revealed as the most operative of the three ones; thus, it may be a useful tool for teaching if we complement it with other data. But, into the context of a pedagogy based on a learner-centred curriculum, any objective selection of lexical contents must be subject to the learner's needs, the classroom negotiation, and the design of communicative learning tasks.