This thesis examines the patterns of stress found in modern Russian inflectional paradigms (nouns, verbs and adjectives), and variation in these patterns. It also examines the 'retraction' of stress onto prepositions before certain nouns and numerals, for example нá день, зá сорок, and onto the negative particles не and ни before the past forms of certain verbs, for example нé дан, нѝ бьіло, and variability in these phenomena. After a detailed survey of literature in the field, a new approach to the treatment of mobile stress in Russian is proposed, called the 'distinctive approach'. This approach takes as its basis not the movement of stress between word-forms, from one morpheme, or one syllable, to another, but rather the patterns of contrasts made by stress between word-forms, and the resulting phonetic realisation of stems. This forms the basis of an original categorisation of the inflectional stress patterns found for nouns, verbs and adjectives, which are examined in detail. Areas of instability in the system are identified, as indicated by the existence of stress variants. Certain of these areas are then further investigated by means of a comparison of dictionary data from standard reference works of the last forty years with new research data provided by a survey of twenty-one Muscovites in the age-range 23 to 62; full tables are given containing the results of this investigation. Each word is then discussed in detail, and a summary given of the changes in stress identified for each word-class. This thesis concludes that there is widespread variation in patterns of mobile stress, and that developments of a varied and disparate nature are taking place in the different parts of the inflectional system. There is, in addition, some evidence that stress mobility, particularly within the sub-paradigm, is being abandoned in favour of fixed stem- or desinence-stress. A reduction in the incidence of stress mobility is also seen in the area of the 'retraction' of stress onto prepositions and negative particles.