Numerous organizations use performance measures to monitor the quality of care provided for a variety of clinical conditions. An appraisal of the evidence underlying such performance measures has never been reported. Our objective was to estimate the effects of interventions recommended by performance measures and to determine the quality of evidence from which those estimates derive, using the Joint Commission and the Centers for Medicare and Medicaid Services' performance measures for community-acquired pneumonia (CAP) as examples. We performed systematic reviews of the literature to identify evidence related to the performance measures for CAP. Metaanalyses were then performed to estimate the absolute and relative effects of the interventions recommended by the performance measures. The Grading Recommendations, Assessment, Development, and Evaluation system was used to determine the quality of evidence. The estimated effects favored the interventions recommended by five of the six performance measures. These included pneumococcal vaccination (incidence of pneumococcal pneumonia: relative risk [RR], 0.43; 95% confidence interval [CI], 0.24-0.75), blood cultures, antibiotic administration within 6 hours, use of a guideline-compliant antibiotic regimen, and influenza vaccination (incidence of symptomatic influenza: RR, 0.30; 95% CI, 0.22-0.40). However, among these performance measures, only influenza vaccination was supported by high-quality evidence. One-step smoking cessation counseling was contradicted by moderate-quality evidence (smoking quit rate: RR, 1.05; 95% CI, 0.90-1.22). The evidence supporting performance measures is frequently not of high quality and occasionally contradictory.