The Global Polio Laboratory Network (GPLN), comprising 145 facilities in 100 countries and operating in all six World Health Organization (WHO) regions, was established in 1988 to support the Global Polio Eradication Initiative. GPLN isolates and characterizes polioviruses from stool specimens of patients with acute flaccid paralysis (AFP), from healthy contacts of AFP patients, and, in some laboratories, from sewage samples. Nucleotide sequences (viral capsid protein VP1 region; 900-906 nucleotides) are determined for wild poliovirus (WPV) isolates from each patient, contact, or sewage sample to target vaccination activities based on the patterns of virus transmission. This report updates previous reports describing GPLN activities and vaccine-derived poliovirus (VDPV) surveillance during January 2007-June 2008. GPLN routinely screens for and characterizes VDPVs, which have caused polio outbreaks in areas with low oral poliovirus vaccine (OPV) coverage and caused prolonged infections in persons with primary immunodeficiencies. Data from GPLN guide the global initiative to eliminate polio. GPLN data are used to confirm polio cases, identify reservoirs of endemicity, determine serotype distributions of circulating polioviruses, detect importations, identify VDPVs, and ultimately document the absence of WPV and VDPVs for certification of polio eradication.