The article presents the political pluralism theory in a context of modern practice of the American political system as well as the principles of its organization. The main stages in development of the concept of the interest groups and the theory of political pluralism in A. Bentley’s, D. Truman’s, R. Dahl’s, Ch. Lindblom’s works are considered The principles of interest groups organization, the main institutional forms and interaction methods of interest groups in the U. S. modern political system are revealed. According to the number of participants, economic and organizational resources and efficiency, the most influential interest groups are determined. The US laws on lobbying regulation and election campaign financing are examined. The article provides statistic data of interest groups» expenses on lobbying and election campaign according to the reports of the Center for Responsive Politics. Autonomous interest groups» activity is an indispensible element of U. S. political framework. Considerable influence of the interest groups on political process determines the importance of the topic.