This study investigates the ways adult second language learners deal with errors and trouble sources in their conversations with one another. Specifically, it describes the repair work done by the second language learners, the extralinguistic features accompanying these repairs and the differences between repairs made by speakers at different proficiency levels. In addition, the repairs made by second language learners of English are compared with repairs made by native speakers. The data were collected from three videotaped conversations between pairs of friends with varying language backgrounds and proficiency levels. Analysis of these conversations showed that the repair work done by the adult second language learners was similar to repairs done by native speakers. However, corrections of beginning second language learners were the outcome of incompetence in phonology, syntax and lexicon. Extralinguistic features were significant in terms of facilitating the process of negotiation for understanding. The three conversations differed significantly according to the students' proficiency level, especially in the pace and length of the repair operations. In general, the data indicate that adult second language learners are able to deal with errors and trouble sources and to learn specifics, such as vocabulary, as well as conversational strategies from conversing with one another. (Author/AMH)