One of the most promising trends in modem political science is the develop­ ment of a theory of politics as rational action. Focussing on choice as the central topic of study, rational choice theorists set out to specify what alter­ native an actor should prefer if he has some given knowledge of the conse­ quences of each alternative and wants to see his preference system as fully realized as possible. But rational choice theory is not confmed to the norma­ tive sphere of science. It can also be used for explanatory purposes. Then, the alternatives actually chosen are specified and the task is to explain the decisions by fmding out what considerations lay behind them. The starting point for an emerging research program at the Department of Government, Uppsala University, on 'Politics as Rational Action' is to describe the major choices in fifteen different policy areas of Swedish domes­ tic politics and explain why they were made.