The monograph continues the series of publications by the Center for Labor Research (CEL) of the National Research University Higher School of Economics, dedicated to the Russian labor market, and offers a comprehensive analysis of the problem of informal employment in Russia. The book discusses the economic nature, sources and mechanisms of formation of informal employment, the main theoretical approaches to its study , existing methods of its statistical measurement. The issue of dualism in the labor market, which involves its segmentation into formal and informal sectors, is examined in detail. The central place in the work is occupied by the analysis of the scale, dynamics and structure of Russian informal employment. Particular attention is paid to the benefits and costs of deformalization of employment relations both for workers and for firms and society as a whole, in particular, differences in wage levels between formal and informal workers are assessed. The impact on informal employment of such institutions as the minimum wage and the taxation system, its contribution to economic inequality, and the dynamics of the movement of workers between the formal and informal sectors are also analyzed. In all chapters of the book, the analysis is carried out using modern econometric methods and using large arrays of microdata. The study allows us to obtain a holistic understanding of the problem of informality in the Russian labor market. For economists and sociologists in the field of labor relations, all those interested in the problems of the Russian labor market. The monograph can be used as a teaching aid when teaching such disciplines as economics and sociology of labor, human resource management.