William Zartman’s concept of ‘ripeness’ has been strongly criticised on both methodological and substantive grounds, yet it remains central to both academic and policy debates. This paper assesses the usefulness of Zartman’s model through an analysis of the three peace agreements which were negotiated during the Northern Ireland conflict—the 1973 power-sharing Sunningdale Agreement, the 1985 inter-governmental Anglo-Irish Agreement and the 1998 Belfast Agreement. It uses a refined version of Zartman’s model to argue that the concept of ‘ripeness’ remains a useful means to analyse the potential for peace and that it can provide an explanation for the relative success of the 1998 Belfast Agreement and for the failure of previous agreements.