Disease caused by influenza virus has been known from ancient times. However, in spite of the progress in pharmacology and vaccinology, this pathogen still affects morbidity and mortality in all age groups all over the world. This article gives some essential information on the history of influenza, its pandemics and main features of influenza viruses. Data on the epidemiologic situation of influenza in Poland in the period 1946-1999 are presented. Influenza surveillance issues and particularly prevention of influenza by vaccinations are discussed.