Recently, there has been a rapid rise in the number of pay-for-performance programs globally that offer physicians and medical groups financial incentives for meeting primary healthcare goals. What market failures do incentives for quality (pay for performance systems or P4P) address? What market failures are incentives for quality (P4P) unable to address? If you were writing a policy paper for the World Bank on pay for performance systems, how would you recommend that the design of these programs be customized to different types of health systems?