Abstract: The incidence and mortality of meningococcal disease have been slowly rising after a 5- year decline from the 1943-44 epidemic.Another trend observed in the civilian pop- ulation is the appreciable rise in the apparent case fatality.Since modern therapy should have reduced the ratio of deaths to recorded cases, indications are that case reporting has deteriorated in recent years.Data are given here to support these observations, to aid in gauging epidemic potential, and particularly to indicate population segments which appear to be at especial risk. General Epidemiological CharacteristicsThe term "meningococcal disease," used at times in this report, includes various clinical forms of the infection, such as meningitis, men- ingococcemia, and milder forms of invasion. Bacteriological TypesThe bacteriology of the' meningococcus is complex, and classifications and viewpoints have changed considerably.The many differ- ent strains of the organism are now commonlv classed into three major groups.Type I ap- parently predominates during heavy epidemics, and types II and IIA, endemically (3a, 16).This raises the question whether publication of current national summaries of types found in