On the ACTFL scale of language proficiency, the Advanced level represents “minimal functional proficiency,” in which a speaker can function in the target language and become a participating partner in the communication (ACTFL Proficiency Guidelines, 1986). While functional competence in speaking is the most frequently cited linguistic goal for studying Russian among students in American universities (Brecht, Caemmerer and Walton, 1995), the transition from Intermediate High to Advanced level in speaking is difficult to achieve within traditional learning environment for English base-language learners of Russian. The present study investigates a range of predictors of gain for the Advanced level resulting from immersion study abroad, by providing a detailed description of pre-program features of a group of learners who had attained a pre-program speaking level of Intermediate High. The study attempts to identify linguistic factors that may predict transition into the Advanced level. Twenty four pre-recorded Intermediate High Oral Proficiency Interviews (OPI) were transcribed, coded, and analyzed by using Child Language Data Exchange System (CHILDES). Areas of interest for coding were based on the components of the widely accepted functional trisection (Higgs and Clifford, 1982): function, content, and accuracy. The speech samples of pre-immersion OPI tests were grouped according to those learners who crossed the Advanced-level threshold on the post-immersion OPI (hereafter: gainers) and those who did not (nullgainers), and this difference provided the basis for prediction which learners would cross this threshold, and which would not. In all the areas of interest: vocabulary, grammar, fluency, error and discourse analyses, pragmatic and sociolinguistic competence, gainers outperformed nullgainers. Three variables were distinguished as the most powerful for discriminating between groups of gainers and nullgainers: vocabulary, fluency, and communication strategies. Results of the study are likely to be of interest for researchers in the field of Second Language Acquisition (SLA), Russian language instructors and those who prepare them, and curriculum and program designers.