Although the reporting process under UN human rights treaties is considered one of the most important universal mechanisms to monitor the implementation of human rights, its actual domestic effects have hardly been studied. This is surprising in the light of the rather extensive work involved and resources spent on the reporting process by states and UN human rights treaty bodies. This article attempts to fill the scholarly neglect by examining the effectiveness of this process in three countries, the Netherlands, New Zealand and Finland. It also explores some more general conceptual, theoretical and methodological issues with respect to the definition and measurement of effectiveness of international (human rights) standards at the domestic level. The empirical results, which are based on extensive document analysis as well as 175 interviews, are used to test two hypotheses based on domestic and transnational mobilization as well as reputational and legitimacy-based explanations. The article especially finds support for the liberalist mobilization thesis, while only limited support is found for reputational and legitimacy-based explanations, at least in established liberal democracies.