Nosocomial transmission of influenza is reported infrequently, but patients in general hospitals are often among the most susceptible to complications of influenza infection. Hospital-acquired influenza may occur more often than is reported, but it may not be recognized because of lack of diagnostic facilities or the time required for virus isolation and identification. Based on mode of transmission in the hospital, established reservoirs of influenza virus and duration of virus shedding, isolating patients with influenza may occasionally be useful but restricting visitors is probably not required. Vaccinating hospital personnel with influenza vaccine and, if influenza A is prevalent, giving amantadine hydrochloride to high-risk patients or personnel should be considered.