The usefulness of explicit knowledge of the second language is a matter of controversy in the field of second language acquisition. In this regard, it has been argued that explicit representations might be useful for some structures but not for others (R. Ellis, 2006; Roehr & Gánem-Gutiérrez, 2009). The goal of this study was to examine whether explicit knowledge about the Spanish subjunctive is related to using this structure accurately in discrete-point measures, as well as in measures of oral and written production. The participants were 46 learners of Spanish as a second language, who were in their fifth semester and had received explicit instruction about the subjunctive during three terms. The results show that the participants had developed somewhat low levels of explicit knowledge of the subjunctive, and that explicit knowledge of this structure was significantly correlated to its correct use in discrete-point grammar exercises and in writing, but not in speaking.