Аннотация:Analysis of morphological and phonetic differences in Ob-Ugric languages correlates with the results of glottochronology calculations conducted on the materials of a survey of native speakers of contemporary dialects.They show that Mansi dialects neither have substantial differences in basic vocabulary, nor did they differ much in morphology and in graphics-phonetics in the 18th century. Phonetic innovations that hindered mutual understanding between speakers of eastern and northern dialects in the 20th century occurred not earlier than 250 years ago.On the contrary, Kazym and Vakh Khanty have more differences than any Slavic and even Turkic (except Chuvash) languages between them. Undoubtedly, they should be accounted for different languages, not dialects. The time of their divergence can be dated as the early as the beginning of the first millennium AD.