This study investigated the extent to which home exposure (HE) to the Chinese language affected the oral proficiency of students of intermediate-level college Mandarin Chinese. In fourteen hypotheses, it was predicted that HEs would perform at a higher level than would non-home-exposure students (NHEs). Students were given a simulated oral proficiency interview, evaluated according to American Council on the Teaching of Foreign Languages (ACTFL) proficiency guidelines. Error analysis of the taped interviews focused on features in five categories: fluency and complexity; phonology; semantics; syntax; and syntax and semantics. Subjects were 6 students with intermediate-level proficiency ratings enrolled in second- and third-year Mandarin courses; three were HEs and three were NHEs. Results confirmed five of the fourteen hypotheses, those relating to patterns in code-switching and errors in vocabulary, tone, pronunciation, and word order. It was found that while the ACTFL intermediate-mid and intermediate-high level criteria seemed to describe the subjects, there were some differences to which the ACTFL guidelines may not be sensitive, particularly the skills of the non-educated but native speaker. Implications for second language instruction are discussed. Contains 31 references. (MSE)