Laboratory diagnosis is important to distinguish influenza from other respiratory virus infections. It will be especially important in detecting the first cases of pandemic influenza. Good quality respiratory tract sampling is needed to maximise diagnostic yield in influenza infection. In the appropriate clinical setting, pandemic strain-specific nucleic acid testing is the initial test of choice for suspected pandemic influenza. It is more sensitive than virus isolation, and more sensitive and specific than serology, immunofluorescence and other antigen detection methods. Virus isolation is needed to monitor new influenza strains and for vaccine development. Analysis of influenza isolates is undertaken by the World Health Organization Global Influenza Surveillance Network. Monitoring for antiviral resistance will be needed with widespread use of neuraminidase inhibitors for treatment and prophylaxis during a pandemic.