The Global Polio Laboratory Network (GPLN) was established after announcement of the 1988 World Health Assembly resolution to eradicate poliomyelitis. Operating in all six World Health Organization (WHO) regions, the network currently has 146 laboratories that test stool specimens from acute flaccid paralysis (AFP) patients for polioviruses. The virologic data provided by GPLN underpin the global polio eradication initiative, guiding decisions regarding where targeted immunization activities should be conducted, based on confirmed wild or vaccine-derived poliovirus circulation. The data also are used to monitor progress toward polio eradication by documenting the genetic diversity and transmission links of viral isolates. This report updates previous reports and describes GPLN performance and initiatives during January 2006-June 2007.