Party regulation has received growing consideration from the scholarly literature in recent years. The increasing attention towards this phenomenon reflects a trend of proliferation in European countries adopting rules which affect political parties in their internal organization, their external activities, or their financial management. Yet, with the possible exception of party finance, comparative research about the different aspects of party regulation is still scarce. This paper collects information on the regulation of political parties in thirty-three European democracies, selected within the framework of the ‘The Constitutional Regulation of Political Parties' and ‘Re-conceptualizing Party Democracy' projects. All country reports follow a similar structure. They describe, where it applies, the provisions referring to political parties in the national constitution, the party law and the party finance law. Particular attention is devoted to key issues such as party registration requirements, restrictions on party activity or identity, thresholds and allocation mechanisms for the public funding of political parties, regulation of private donations, as well as to the institution of authorities for the external oversight over the political parties' activities.