"This paper analyzes how the future tense is associated to the subjunctive in the relative clause with the implicit antecedent cuando. A revision of the bibliography is offered, and the analysis focuses especially on a survey carried out with different questions about the mood and tense of the main verb in the free relative clauses of person, place, mood and time. This survey was conducted with 52 Spanish-speaking cultured informants; their choice preference of the verbal form, which is confirmed by an analysis based on the CORPES and CREA, leads us to the conclusion that the case in question shows some peculiarities which are distinguished from other relative clauses, in that the future tense is incompatible with the subordinate clause induced by cuando even if the time frame to which the adverb cuando is related has been previously presented. Furthermore, the future tense in the main clause is related to the subjunctive in the subordinate clause, so much so that its appearance in the main sentence determines the use of the subjunctive in the subordinate clause."