This doctoral thesis focuses on Russian-English bilingualism and code-switching in New York and is based on a field-study Esma Gregor conducted between 1998 and 2000 in New York City. Consisting of several parts, the thesis begins with a discussion of the methodological framework used by the author and subsequent problems encountered during the field-study. Subsequent parts focus on Russian immigration to New York City and details the current linguistic situation of the Russian-speaking minority in New York. The greater part of the thesis, however, focuses on a discussion on the main functional models in code-switching research, and applies them to the data gathered in the field-study. In a subsequent analysis of the field-work, the results are quantified and an attempt is made to correlate the linguistic competence of the speakers with their code-switching behavior.