This thesis studies the impact, determinants, organization, internal dynamics and characteristics of Dutch cartels during a period in which most cartels were legal. We concentrate on the legal-cartel era defined as the period 1935–1998 wherein the Dutch legislation was cartel friendly. The first explicit cartel-friendly legislation dates back to 1935. It was only in 1998 that cartels became prohibited according to section 6 of the Dutch competition act. From 1941 until 1998 cartels were required to notify the Ministry of Economic Affairs of their anticompetitive agreements and provide detailed information in the so-called cartel register. The primary data from the Dutch cartel register, containing the Dutch cartel notifications, are disclosed in this thesis and form the basis and novel major contribution of this research. _Chapter 2_ discusses the social, legal and economic transformation processes from the legal-cartel era in the 1930s to the anti-cartel regime in the late twentieth century. For four distinctive periods of the legal-cartel era ((i) cooperation and cartels, (ii) modification, (iii) institutional inertia and (iv) transformation), we examine national and international developments and institutional and regulatory change. _Chapter 3_ sheds light on the degree and nature of registered cartelization in the Netherlands in the 20th century. Chapter 3 provides a quantitative substantiation of chapter 2. _Chapter 4_ investigates the effects of cartel activity on Total Factor Productivity (TFP) growth. A fixed effects panel analysis for 27 industries of the Dutch economy in the period 1982–1998 is conducted to test whether the presence of cartels had impact on TFP growth. Our research results suggest that cartel presence, indicated by registration status in the cartel register, curbs TFP growth at industry level of the Dutch economy in the period 1982–1998. _Chapter 5_ examines twelve characteristics of legal cartels in relation to their duration. We conduct a time survival analysis for 667 legal cartels ...