These data form a part of a longitudinal study of vowel system formation for Russian language. The goal of this investigation is to examine the process of vowels spectral characteristics dynamics from child speech to the corresponding values in normal Russian adult speech. The vowels from vocalizations and words of 5 Russian children from 3 to 60 months of age were analyzed. The spectral features of the vowels recognized by native speakers as corresponding Russian phonemes were taken into account. It was shown that the formants characteristics do not correspond to those in adults' speech yet, but they differ from vowel to vowel at 3-5 years of age. Many sounds at each age are impossible to describe by means of classical acoustic keys, but native speakers attributed these sounds to certain categories with high probability. To describe these sounds we use an additional system of distinctive features.