Antiviral therapy against influenza requires the beginning of treatment within 36 to 48 h after the onset of symptoms. With the availability of the neuraminidase inhibitors which are effective against influenza A and B a rapid diagnosis of influenza is of increasing interest. A diagnosis during the first consultation would be ideal for treatment. This can be achieved with clinical diagnosis and with quick tests that can be conducted in the practice (point of care test). The costs of such virological examinations have to be considered in relation to the use of information they create. The cost benefit relation is discussed in relation with different epidemic situations. The benefit and additional information of tests for individual diagnosis is high when the incidence of influenza is low, while in periods with high incidences the clinical diagnosis alone appears sufficient.