Because of the significant mortality rate and sometimes serious neurological sequelae, pyogenic bacterial meningitis continues to be a serious infection despite of the availability of effective antibiotics. Laboratory diagnosis, on the basis of bacteriological study in particular, is an essential procedure not only for the determination of etiology but also for the selection of proper antibiotics. An analysis of the bacterial and fungal isolations during the years 1970-74 at Yonsei University Medical Center was made to draw the following summaries. 1. Fifty three bacteria and one fungus strains were isolated : of which 60.1% were S. pneumoniae, N. meningitidis and H. influenzae. Isolates include one strain each of B. alvei and C. neoformans. 2. Culture positive patients were most frequently those who belonged to an age group of 1month-1 year. 3. H. influenzae was isolated from Patients upto 2-4 year old group and N. meningitidis upto 20-29 year old group, while S. pneumoniae was isolated from young and from old groups 4. Male to female ratio of culture positive patient was approximately 2 : 1. 5. N. meningitidis was isolated from winter to early summer months and S. pneumoniae and H. influenzae from autumn to spring months. 6. Some of the patients from whom opportunistic pathogens were isolated had injuries or operations on their heads. Some had bacterial infections on other part of their bodies. 7. Few isolates of N. meningitidis, S. pneumoniae and H. influenzae showed in vitro resistance to some of the tested antibiotics.