On the observation that desinence allomorphy in Russian, one of inflecting languages, is differently distributed between the two numbers (Singular vs. Plural), this study proposes for the theory of inflectional morphology that there are three main guidelines for the establishment of inflection patterns: (1) similarity in the formal constituency of the inflectional paradigm, (2) distributional dependency among desinences belonging to one and the same paradigm, and (3) motivated minimal difference. This proposal is argued to remedy (1) Zaliznjak`s methodology of establishing agreement class on the form-al basis and Corbett`s suggestion of the relation between gender and inflection class and (2) the definition given in Aronoff (1994) and Carstairs-McCarthy (1998) of the inflection class and pattern.