Environmental policy integration (EPI) has been broadly embraced as a principle in European policy making. Yet, what it means in practice is far from clear and its translation from rhetoric to action has been shown to be complex and politically difficult. This paper provides a conceptual clarification of EPI based on a review of current research. It then develops an analytical framework for analysing EPI from a policy networks perspective, with a set of variables based on existing theoretical and empirical research. In explaining EPI, the analytical framework focuses on policy-making rules and assessment processes as independent variables, but includes background factors such as problem characteristics and the international policy context. The framework is tested in a preliminary study of EPI in energy policy making in Sweden, and some elaborations to the framework are suggested based on the empirical findings.