Party ethics regulations are critical in framing the ethical climate in which political parties operate. These can be imposed by law for all parties, or voluntarily adopted by political parties to set, oversee, and enforce standards of conduct to their members. Much of the literature is case studyoriented and deals with system-level regulation, traditionally covering registration, financing, and internal governance issues. Theoretical work and comparative empirical research on party ethics self-regulation is less developed and remains a blind spot in existing databases of party politics. This project contributes theoretically and empirically to our understanding of political parties’ efforts to address ethical issues within their organizations. To do so, it will expand the Party Ethics Self-Regulation (PESR) database to political parties with parliamentary representation in other democracies beyond Europe through the use of an institutional profiling questionnaire. Drawing on this comparative data, we will develop a multidimensional index to measure the degree of party ethics self-regulation across democracies by focusing on three fundamental and interdependent regulatory dimensions: (i) standard-setting; (ii) oversight; and (iii) enforcement. Regression analysis is then used as a preliminary test of the conceptual strength and usefulness of the PESR index and to uncover associations between these measures and a range of factors that can potentially explain differences in results across parties. We will then complement this cross-country mapping with an in-depth comparison of four cases, theoretically informed but resulting inductively from the comparative analysis. We will identify four parties where PESR has been adopted, either voluntarily or as a legal requirement, to mitigate reputational risks associated with unethical conduct with three independent variables in mind: the degree of party institutionalisation, the level of party system fragmentation in parliament, and the perceived levels of political corruption in the country. These criteria might be adjusted in response to the findings of our regression model. We will interview the party representatives/officials to learn about these reforms have been put into practice and with what degree of consistency. Finally, we will conduct an exploratory experimental study using conjoint analysis to test how each of the three dimensions of party ethics self-regulation can impact on voters’ choices, which will act as a proxy of the consistency and success of these reforms.