INTRODUCTION. Bacterial meningitis (BM) is one of the most severe clinical form of infections, which is well known for an acute course and high mortality. Therefore, it is crucial to establish the etiology and antibiotic susceptibility of frequently isolated microorganisms. AIM. The aim of this study was to present the etiological agents of BM in adults and antibiotic susceptibility of Streptococcus pneumoniae. MATERIALS AND METHODS. The inpatient medical records with positive results of the cerebrospinal fluid (CSF) samples obtained from the patients of Regional Specialist Hospital of dr Wł. Biegański in Łódź between January 2009 and January 2016 were analyzed. RESULTS. In total 1303 CSF samples were taken from 863 patients during this study period, of which 130 CSF specimens were positive for bacterial growth. However, 29 of them were recognized as the contamination and rejected. Therefore, 101 bacterial strains isolated from the CSF samples of 96 patients were analyzed. Five patients had the recurrence of BM. S. pneumoniae was the predominant isolated species (36 strains, 35.6%) which antimicrobial susceptibility results were presented. CONCLUSIIONS. S. pneumoniae was the most common etiological agent of BM in both patient age groups: adults aged >50 years and adults aged 20-50 years. N.meningitidis was isolated most frequent from patients ≤50 years, while S. aureus and Gram-negative bacilli were obtained mainly from group > 50 years old. All tested strains of S. pneumoniae were sensitive to vancomycin, linezolid, levofloxacin, rifampicin and chloramphenicol. High percentage of fully sensitivity to ceftriakson (97.2%) and meropenem (96.4%) was observed. Resistance to penicillin was detected in 27.8% of all strains.