The paper considers those positive moments that were achieved in the works of N.S. Trubetskoi in morphonology, as well as the disadvantages that did not allow morphonology to be distinguished as an independent linguistic discipline. The views of N.S. Trubetskoi were further developed by the Prague Linguistic School. However, they failed to resolve the issue of the independent status of morphonology as a linguistic discipline, although they tried to single out independent morphonological units – morphoneme and alternant.