Sickness insurance (SI) systems are part of the welfare state. This chapter focuses on the characteristics of the SI systems and their direct effects, or what one could call the narrow causal loop. It explores the respective roles of public and private institutions and organizations in sickness insurance. Sickness insurance systems are again alike, but with interesting variations, partly in response to the divergences of welfare states, partly for specific, historical reasons. The Finnish welfare state has historically developed under a much stronger influence from agrarian interests. The development and character of the Finnish SI system was related to the political power of the Agrarian party and farmers associations. Sickness insurance, or more broadly, the provision of income during sickness, is one important facet of the welfare state. The SI systems are no longer residual, and in terms of the dual welfare state, they belong to the institutional side.