Epilepsy and pregnancy registries have been operational for more than 10 years, have accrued considerable experience, and collected an impressive amount of data. As findings have been published, it has become important to understand how observations from the different registries are comparable, especially since their methodologies differ somewhat. In September 2008, representatives of the UK Epilepsy and Pregnancy Register, the North American AED Pregnancy Registry (NAAPR), and the European and International Registry of Antiepileptic Drugs in Pregnancy (EURAP) met for a workshop. Their objectives were to exchange information on their methodologies and to discuss areas where harmonization might be possible. This report summarizes these discussions.