Although on an individual basis and for some selected closed groups immunization against influenza has proved its value over the last 30 years, it has not resulted in prevention of epidemics. The impact of vaccination on national morbidity and mortality statistics has been disappointing. The reasons for this apparent failure of disease control by immunization are discussed. It is concluded that influenza vaccination has not been practised on a large enough scale to achieve an obvious effect on the spread of the viruses in open communities. The groups of people who deserve special attention in order to minimize the damages caused by influenza epidemics are considered. Advantages and disadvantages of available types of vaccine, methods and routes of administration are assessed. It is suggested that systematic application of present knowledge would probably have more impact in the near future than efforts to increase vaccine efficacy. The main current deficiencies are identified as the difficulty of producing adequate supplies of properly constituted vaccines at short notice and the general reluctance to accept annual large-scale immunization programmes. In the view of the authors these logistic and administrative problems could be resolved by long-term coordinated planning between relevant authorities and vaccine manufacturers.