The course deals with a few topics related to the intervention of the State in the economy; the approach follows the the framework provided by the contemporary public economics view, and has a special focus on the Welfare State. After a brief presentation of the main microeconomic tools, the course will be developed in two steps. In the first, that has a preliminary/introductory function, a few basic concepts will be reviewed: Paretian efficiency, market failures, theories of social well-being. In the second, the theoretical-institutional aspects of public spending in the Welfare State will be addressed: special attention will be given to the social expenditure programs (healthcare, social security, welfare programs, education) and their foundations, which differ from those of the public interventions characterising the Liberal State (public order, justice administration, national defense, etc.).