This is a review of present knowledge about the chances of preventing otitis media (OM) by vaccination. Studies of experimental pneumococcal OM in the chinchilla, and observations on serum antipneumococcal antibody levels in children in connection with OM morbidity suggested that protective immunity could be achieved by vaccination. On the other hand, many of the pneumococcal polysaccharides--including those four types that are most common in OM--are not highly immunogenic in infants younger than 2 years. The highest incidence of OM coincides with that very age of low responsiveness. Four large field studies in USA and Finland have shown that vaccination with 14-valent pneumococcal vaccine does prevent recurrent as well as first-time OM caused by species to which good immune response is obtained. Because the most common pneumococci do not belong to this category, the overall protective effect of such vaccination remains low (10 to 15% in the studies reported). Thus the present vaccine cannot be recommended for prevention of OM in infants younger than 2 years. The data strongly encourages efforts in vaccine development, in ways that improve immunogenicity in infants.