There is increased awareness of the power of public procurement to shape supply and to thereby influence a whole array of economic factors. This background paper emphasizes the role of competition in public procurement. Substantive and institutional aspects of public procurement systems are discussed, including strategies to broaden the circle of potential bidders, to incentivize competitive behaviors and to fight bid rigging. The paper also aims at initiating and provoking further discussion on applied issues, on bid rigging prevention, detection and enforcement as well as to share learnt lessons on policy frameworks and procuring practices that effectively promote competition in procurement markets.