The results obtained in the examination of patients with meningococcal infection during the period of 1980-1985 are analyzed. The increasing role of serogroup B meningococci in the etiology of the generalized forms of infection, especially in children aged under 3 years and in adults over 50 years, is shown. As noted in this investigation, the disease induced by group B meningococci runs a more severe course. Morbidity caused by this serogroup of meningococci does not result in epidemics in our country. The distribution of patients among different age groups and specific features of the clinical course of the disease in connection with the serogroup of the causative agent make it possible to regard the risk groups as groups with decreased reactivity, which raises doubts concerning the possibility of forming effective postvaccinal immunity against group B meningococci in such persons.