Acomprehensive understanding of international environmental politics re quires attention to foreign policy. In this essay we describe a wide range of theories and approaches to foreign policy and international relations, with emphasis on how they can help us to better understand foreign policy in the environmental issue area. We organize the theories into three categories: systemic theories, which emphasize the influence of the international system, including the distribution of power within it; societal theories, which focus our attention on domestic politics and culture; and state-centric theories, which find answers to questions about foreign policy within the structure of the state and the individuals who promulgate and implement foreign policies in the name of a given country. Within this presentation of various theories, we highlight the influence of power, interests and ideas.