This thesis seeks to understand, and evaluate, the contribution of business associations within the United States (US) and German chemical sector, to the effective regulation of nanomaterials. In the effective regulation of new technologies characterized by high scientific uncertainty, with nanomaterials being an example of such a technology, it is useful to diverge from the traditional perspective on effective regulation. Rather than focusing on the outcome of rule compliant behavior in order to determine the effectiveness of regulation, it is more useful to investigate processes of learning that prepare for rule compliance. Associations can prepare compliance for companies with the legal obligation to conduct risk assessment for nanomaterials by making available, and extending, scientific data in collaboration with regulators. On this basis associations can develop guidance material (i.e., soft regulation) in order to support their members companies in conducting risk assessment for nanomaterials. A theoretical framework is developed that adopts three learning types: substantive learning (with the key characteristic ‘scientific expertise’), strategic learning (with the key characteristic ‘trust’), and institutional learning (with the key characteristic ‘rules’). Conditions under which these three learning types emerge are derived and used to empirically analyze and compare business association contributions to effective nanomaterials OHS regulation in two case studies: the American Chemistry Council’s (ACC) Nano Panel and the German Chemical Industry Association (VCI). Association collaborative activities are investigated through qualitative, semi-structured interviews with involved stakeholders and through publicly available (policy) documents supporting association activities. The empirical results indicate that the two associations have facilitated learning–to varying levels–relevant for preparing compliance of companies with existing OHS legislation. Overall, the VCI activities facilitated strong learning while the ACC Nano Panel facilitated limited learning. This thesis finds that for learning processes in collaborative activities among business associations and regulators it is important that relationships among collaborators are characterized by trust so as to facilitate knowledge exchange/generation and joint rule development. To prevent capture of public regulators, it is recommended that an independent body, responsible for identifying and communicating the goals of the involved actors, oversees the collaboration. Suitable bodies are federal research institutes.