The work sheds light on the most prominent contribution of the northern European member states to the evolution of European law: the improved acknowledgement and recognition of the principle of transparency of governmental and other state actions. Subject of this thesis is the historical development of this principle in the northern European states as well as the general particularities of those jurisdictions. The core of the thesis contains a systematic analysis of the evolution of the principle of transparency in the relevant decisions of the European courts, in the fields of institutional law, anti-trust law, and environmental law. The different individual rights and claims are systematically evaluated and the limits of the principle of transparency are highlighted. The thesis concludes with an outlook on future developments.