This article explains the variation in policy design processes and the resulting policy-outputs of ‘biopolicies' implemented within the domain of Assisted Reproductive Technology (ART) for eleven European and North-American countries. By applying the method of Qualitative Comparative Analysis, the comparison describes and defines the ‘multiple conjunctural causation' to explain the divergences or similarities of ART policies in Europe and North America. The policy preferences of the actors involved in the relevant ART policy network and the institutional rules characterizing the respective polity need to be considered together in order to explain why different countries adopted similar or different ART policies. In particular, the analysis stresses the influence of party politics, the self-regulation of ART by the physicians, the mobilization of interest groups, the number of institutional arenas involved in the designing process and the nature of decision-making rules (power-sharing versus majority) on the designing processes and the resulting policies. Thus, different policy designs are linked to different designing processes, encompassing four ideal-typical decision-making modes: ‘designing by non-decisions', ‘designing by elites', ‘designing by accommodation' and ‘designing by mobilization and consultation'. These results shed new light on the challenges for developing a policy design theory that could provide a robust framework for describing and explaining policy formulation.