This thesis analyses how environmental non-governmental organisations (ENGOs) operate to influence national environmental policy making in different structural and cultural contexts. It does so by first identifying what type of strategies ENGOs in Norway and Argentina employ to achieve their goals. It thereby seeks to explain differences and similarities in the use of strategies in, and between, the two countries based on three explanation variables; political structure, political culture and organisational characteristics. The thesis is based on the assumption that because there are big differences between the countries in relation to these variables, we can expect to find notable differences also in the strategies that the ENGOs employ to influence national environmental policy making.The analysis concludes that the differences in ENGOs’ choice of strategies between Norway and Argentina are not as prominent as expected, and that organisations in both countries employ a wide range of strategies to influence on the decisions of policy makers. The main difference that was found is that ENGOs in Argentina to a lesser degree than ENGOs in Norway employ conventional strategies that require initiation by the public authorities. Disparity in the political structures of the countries was identified as the most important reason for this discovery. Also organisational characteristics, operationalised as experience and values, proved to play an important role in determining what type of strategies ENGOs in both countries employ.Political culture helps us to understand nuances in the employment of strategies, but does in itself not explain differences in ENGOs choice of strategies between the countries. This is largely due to great diversity in activities between organisations within each country.