<p>The purpose of this study is to present a summary of morphosyntactic variation and a detailed analysis of the phenomenon of preposition drop in the Russian speech of Chuvash bilinguals. Specifically, I investigate what underlying factors might condition the variation. I conduct a qualitative analysis of the data extracted from the corpus of Russian spoken in Chuvashia to overview morphosyntactic peculiarities and then present a qualitative case study of preposition drop. The case study involves all 2529 preposition phrases found in the corpus. I implement statistical modeling to discover what possible factors might condition preposition drop. The results of this research show that the morphosyntactic system of Chuvash Russian includes many features previously attested in other contact varieties of Russian, such as non-standard assignment of number and gender, non-standard functions of the nominative case (some of which are unique to Chuvash Russian), and preposition drop. I conclude that preposition drop may be caused by phonotactic constraints, morphosyntactic interference with the Chuvash language, and the lack of semantic markedness of certain prepositional phrases.</p>