The results of 2 large field studies on the impact of the polio eradication initiative on health systems and 3 supplementary reports were presented at a December 1999 meeting convened by the World Health Organization. All of these studies concluded that positive synergies exist between polio eradication and health systems but that these synergies have not been vigorously exploited. The eradication of polio has probably improved health systems worldwide by broadening distribution of vitamin A supplements, improving cooperation among enterovirus laboratories, and facilitating linkages between health workers and their communities. The results of these studies also show that eliminating polio did not cause a diminution of funding for immunization against other illnesses. Relatively little is known about the opportunity costs of polio eradication. Improved planning in disease eradication initiatives can minimize disruptions in the delivery of other services. Future initiatives should include indicators and baseline data for monitoring effects on health systems development.