The aim of the article is an attempt to ground the concept of transformation of national institutional environment as the prerequisites for forming of prosperous class of small and medium-sized enterprises. Institutional analysis considers the interaction on the level of individuals and divides a market transaction into transactions (institutional agreements), estimating their value with the help of transaction costs. We conducted a systematization of the notion that brings the institutional environment to the aggregate of norms, regulations, agreements, rules of the game. For the quality assessment of institutional environment on the macrolevel, direct indicators of its assessment were used - quality indexes in international ratings and activities of specialized institutional researches. Practical significance. In the result the quality of the institutional environment of the assessment of The Global Competitiveness Index is extremely low and needs a systematic increase. Values of indicators of a pillar "Institutions" of The Global Competitiveness Index should be a guiding line for development and introduction of state economic policy. An important line of investigations of development mechanism's improvement and regulatory policy's conducting is the institutional environment conception that combines the notions of institute, institutional agreements and transaction costs. A model of institutional environment allows determining of the regulatory policy as a policy that changes elements of institutional environment - institutions, displays in changes of transaction costs. It is grounded that a state apparatus consciously sets as an object the increase of socio-economic role of the entrepreneurship through the creating of favourable conditions of its functioning; a way of this object's achievement is the regulatory policy, efficiency criterion of which is the improving of national institutional environment's quality that is measured by reducing of transaction costs of entrepreneurship subjects. All stated above allows describing the mechanism of regulatory policy in the field of entrepreneurship as a logical order. Measures of regulatory policy influence the quality of institutional environment that leads to the change in transaction costs' value related to its use. A schematic model of modern institutional environment is developed. In accordance with the rules of methodological individualization, subjects of institutional economic relations are separate entities, individuals. Subjects implement among themselves standard institutional agreements, which are presented by lines ("tracks"). These "tracks" necessarily go through formal and informal institutions. Conclusion of institutional agreements is the choice among the institutional alternatives, discrete choice and transaction performance. Some institutions (both formal and informal) can be not involved into conclusion of institutional agreements, thus it is the question of institutions market - subjects' possibility to choose institutions for interaction. Subjects can conclude institutional agreements within the framework of company or state (hierarchies of institutions with certain cruelty) or within the framework of market (relatively soft institution). An important socio-economic role of small and medium-sized enterprises must be confirmed by effective public policy with its support and development. Institutional economic analysis provides the possibilities of qualitative research of problems of small and medium-sized enterprises, developments and introduction of regulatory police, determining of the criteria of its efficiency. The use of system model of institutional environment and principle of methodological individualism allows considering the economic interaction between representatives of small and medium-sized enterprises and state. An increase of institutional environment quality is the main task of regulatory policy. The quality of Ukrainian institutional environment by the criteria of international rating Doing Business in comparison with the leading countries during 2007-2013 not exceeded 27%. A criterion of regulatory policy effectiveness in the model of institutional environment is a cheapening of institutional agreements, i.e. transaction costs decrease that leads to increase of socio-economic effectiveness of small and medium-sized enterprises.
