This paper offers a critical review of the theoretical literature on the relationship between the production of scientific knowledge and its use in policy formulation and implementation. Extensive academic output, using a diversity of approaches and analytical frameworks, has sought to systematize knowledge transfer categories and strategies with a view to improving the application of scientific knowledge. A considerable part of this thinking addresses the problem from a more traditional perspective, which (explicitly or implicitly) regards research results as an "accumulable product", depicts the decision-making process simplistically and linearly, and thus restricts strategies to the suiting of research endeavors to needs. Newer approaches place greater importance on the complexity of policymaking and the knowledge production process, which are integrated into and explained in particular political and institutional settings. Although the application of knowledge transfer ideas to health policy and systems research does generate some interesting contributions, a long process of theoretical thinking lies ahead.