Surzhyk is a stigmatized Russian-Ukrainian language variety spoken in Ukraine. Although several authors have conducted research on Surzhyk, an agreed-upon classification of this language variety has not been found. Scholars classify any combination of Russian and Ukrainian elements in the same utterance as Surzhyk. Having classified spoken data that combined Russian and Ukrainian language juxtapositions, I identified what constitutes Surzhyk Proper and what are cases of Russian-Ukrainian codeswitching and lexical borrowing. Surzhyk Proper has a systematic internal structure. Its morphosyntax is supplied by Ukrainian, while lexical items are supplied either by Ukrainian or by Russian.