A prospective study was conducted to find the incidence and clinical manifestations of influenza in 201 nurse assistant students of Faculty of Tropical Medicine during June 1998 to May 1999. There were 106 episodes of influenza-like illness (incidence 52.7%) of which only 33% were proven to be influenza (incidence 17.4%). Main clinical manifestations of influenza included headache, fever, malaise, myalgia, rhinorrhea, cough, and sore throat. We found that influenza could not be diagnosed solely by using clinical manifestations. Respiratory pathogenic bacteria were rarely isolated in patients with influenza-like illness and this led to our suggestion that routine pharyngeal culture and antibiotic therapy would not be helpful. Influenza vaccination of every nurse assistant student would be beneficial.