The regulation of occupations is widespread, extending beyond the liberal professions, such as lawyers and engineers, to a broader set of other economic activities. Competition authorities have long been active in improving competition in these markets, both through enforcement action and by advocating to make regulation more pro-competitive. This paper aims to support competition authorities’ advocacy efforts. It includes an overview of the literature about the effects of regulation of professional services, which competition authorities can draw on to advocate for the benefits of less restrictive regulation where appropriate. The paper also brings together analytical frameworks developed by the OECD and jurisdictions such as Australia, the US and EU to assess regulatory barriers to competition. The paper further draws on case studies of advocacy efforts from competition authorities across a range of OECD member countries.