A central issue in the ongoing negotiations towards a new international climate change agreement this year in Paris is how the agreement will differentiate obligations among developed and developing countries. Differentiation among parties to the United Nations Framework Convention on Climate Change, based on their “common but differentiated responsibilities and respective capabilities,” is a defining feature of the international climate change regime. This policy brief outlines the basis for and forms of differentiation in the climate regime, and the key areas where differentiation has arisen in the negotiations for a 2015 agreement. The brief then presents a range of design options, drawn from the climate regime as well as other multilateral environmental agreements, for differentiation in the 2015 agreement. It concludes that the most feasible approach is likely to be a hybrid one that tailors the manner of differentiation to the specific elements of the agreement.