Several studies have shown that phonetic and phonological categories of both languages interact in bilingual speakers [e.g., speech learning model; Flege (1995)]. Interestingly, these categories continuously change over a period of time, drifting toward the characteristics of the ambient language. [Sancier and Fowler (1997)]. In this study, we studied how categories change in a short term bilingual interaction. Specifically, we were interested in whether cross linguistic influences were moderated by the extent of concurrent use of the two languages as well as the linguistic abilities of the target audience. To examine these questions, we recorded the production of Spanish language instructors. Their productions were studied before, during, and after a classroom interaction to determine changes in production. Furthermore, these productions were recorded in Spanish language courses of varying levels to determine specifically whether there was an increased influence of Spanish phonology on English productions in higher-level courses. The speech samples were phonetically transcribed and analyzed. Acoustic analyzes were performed to detect changes in voice onset time [Lisker and Abramson (1964)], vowel space, consonant manner class, and stress patterns. This study has implications for theories of bilingual speech production as well as for second language instruction and education.