This doctoral thesis focuses on RussianEnglish bilingualism and codeswitching in New York and is based on a fieldstudy 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 fieldstudy. Subsequent parts focus on Russian immigration to New York City and details the current linguistic situation of the Russianspeaking minority in New York. The greater part of the thesis however focuses on a discussion on the main functional models in codeswitching research and applies them to the data gathered in the fieldstudy. In a subsequent analysis of the fieldwork the results are quantified and an attempt is made to correlate the linguistic competence of the speakers with their codeswitching behavior.