Antimicrobial treatment of bacterial meningitis should be done by antibiotic to which the causative agent is susceptible, which attained serum levels ensure adequate penetration across the blood-brain barrier and which bactericidal levels in cerebrospinal fluid are achieved. A total number of 61 child in age from 2 months to 7 years with bacteriologically proved Haemophilus influenzae meningitis was included in the study. The possibility and usefulness of application of various antibiotics used in the treatment of this disease as well as the results attained have been discussed. A total number of 40 patients was treated with only one antibiotic (ampicillin 6, chloramphenicol 6, cefuroxime 3, cefotaxime 18, ceftazidime 7) and 21 patients were treated with combinations of antibiotics (ampicillin + chloramphenicol 14, cefuroxime + chloramphenicol 7). The causative agent was susceptible to the applied antibiotic in all cases. The agent susceptibility was estimated qualitatively by disk diffusion method and quantitatively by methods of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Even 31.1% of H. influenzae strains were resistant to ampicillin. Penetration across the blood-brain barrier was monitored by estimation of antibiotic concentration in sera and liquor. Antibiotic concentrations in liquor attained the bactericidal levels. The same good results were attained with any of single applied antibiotics. In cases of delayed initiation of the antimicrobial therapy the appearance of neurological complications was more frequent, the outcome of the disease was worse and the duration of treatment was longer.(ABSTRACT TRUNCATED AT 250 WORDS)