This chapter looks at successful knowledge transfer of products or processes from public research organizations to private sector firms for commercialization. Through six national case studies (Germany, the Republic of Korea, and the UK for high-income countries, and Brazil, China, and South Africa for middle-income countries), contextual conditions that influence success are discussed. Over time, the conceptual model behind policies to support knowledge transfer has shifted from a mode 1 linear pipeline model to a mode 3 model. In the linear model, basic research conducted by universities is followed by applied research, either by public research organizations or firms. In a mode 3 model, multiple actors – such as different types of public research organization, knowledge intermediaries such as knowledge transfer offices, and private businesses – are involved in an innovation system; there is a reverse knowledge flow whereby firms provide public research scientists with information on their needs, which influences the research projects of public research scientists. Best practice includes policy support for research and development and other innovation-related activities and incentives for firms to work closely with public sector researchers for problem solving and commercialization.