In work it is shown that the category «cluster» was strongly enshrined in modern scientific and practical activities of Russia. Moreover, the resistant tendency of the subsequent development of the relevant legislation is observed. However due to the lack of accurate scientific and legal study of essence and signs of clusters lack of uniformity in their standard maintenance is observed. It is noted that being complex and capacious concept, «cluster» is defined by various scientists-researchers as: geographically close groups of companies specializing on production of similar products or rendering services; geographically close group of the interconnected industries; networks of the enterprises and organizations and the related institutions within geographical boundaries; groups of companies, using identical production technologies and connected with other groups of firms on the basis of technology. Special relevance to this problem is given by that fact that budgets of various levels allocate considerable financing for creation and development of clusters. Therefore, need of formation of bigger definiteness for understanding of known category is dictated not only theoretical interests, but also the purpose to exclude possibility of an inefficient expenditure of budgetary funds. It is noted that the name of cluster initiatives was steadily assigned to actions for activation and development of a cluster in literature. A cluster initiative – set of actions, programs, the projects aimed at development of this or that cluster (clusters). It is shown that the clustering of economy allows to create a complex view of a state policy of regional development, to increase productivity, efficiency and competitiveness of business, to expand opportunities for innovative development, to optimize interaction between various subjects of economic development of the region: state, large and small business, scientific and educational community and public; to increase quality of life of the population. Authors stated cluster initiatives of regional development of economy and results of the analysis of cluster development of regions of Russia and cluster structure of economy of St. Petersburg are presented. Besides, institutes and instruments of support and development of cluster initiatives in Russia are considered.