Although based on the literature, one could assume that regressive harmony occurs at least marginally, VH is always progressive in Uralic languages.

Cyganov (1959) mentions that the Erzya dialects spoken in Ardatovsky rayon (the only district of Mordovia bordering Chuvashia) and Chuvashia exhibit regressive assimilation: alternating /o/ and /e/ are replaced with /u/ and /i/, respectively, before syllables with /ɑ/. However, since in this case mid vowels are replaced by high ones before a low vowel , this is clearly a regressive dissimilation process, therefore it cannot be analysed as vowel harmony.

In addition, there are some languages in which the vowel of the initial syllable alternates, and at least historically — with some degree of certainty — depending on the quality of the vowel of the second syllable. However, synchronically we cannot speak about vowel-vowel interactions in any of these cases.  Such languages are Livonian (Kallio 2016: 51–54), Pite Saami (Wilbur 2014: 78–81), Lule Saami (Tamás 2006), and Eastern Khanty (Tereshkin 1961: 20–23 for Vakh, Filchenko 2007 for Vasyugan, Csepregi 1998: 17–18 for Surgut Khanty.)