The presence of measles specific antibodies is usually taken as evidence of typical measles in the past; in the present study it was regarded as evidence of infection with measles virus, but not necessarily of the common disease accompanied by a typical rash. The association between a negative history of measles in childhood and certain diseases later in life was investigated by a historical prospective method, based on school health records combined with self-reporting in adulthood, and tests for specific IgG measles antibody. There was evidence of association between a negative history of measles, exposure in early life (possibly injection of immune serum globulin after exposure), and development of immunoreactive diseases, sebaceous skin diseases, degenerative diseases of bone and cartilage, and certain tumours. It is suggested that the presence of measles virus specific antibodies at the time of acute infection interferes with development of specific cytolytic reactions, and enables intracellular measles virus to survive the acute infection. If this hypothesis is verified, use of immune serum globulin after measles exposure has to be of immune serum globulin after measles exposure has to be reconsidered.