This case study investigated spontaneous interpersonal communication in a high school Spanish classroom, using instructional conversation as a framework for analysis. Instructional conversations are collaborative, extended verbal exchanges in which students develop a coherent topic, supported by the teacher's contingent questions and feedback. The features, length, and frequency of instructional conversations were examined. Analysis of discourse led to a set of distinctive features adapted from the bilingual instructional conversation model. Seventeen instructional conversation episodes constituted 7% of the total time in 18 observed lessons, occurring typically before the teacher's planned lesson activities and at transitions in the lesson. The potential value of instructional conversations for developing interactional competence suggests that they deserve the attention of teachers and researchers, and a more prominent place in the language classroom.