Reciprocal peer tutoring can be an effective supplement to teacher-led instruction, but students need to have the tutoring skills necessary to teach their peers successfully. Previous studies have addressed the challenge of providing essential information to a naive tutor, allowing for correct modeling and feedback. The present study compared incidental learning of vocabulary words through classroom reading instruction to a combination of incidental learning supplemented with peer tutoring. Eight fourth-grade students were trained to tutor each other using a digital recording and playback device that provides audio prompts to naive tutors. Results indicated that students made modest gains from incidental learning and much stronger gains from peer tutoring with audio prompting. Implications for practice and future research are discussed. (Contains 3 tables and 2 figures.)