We conducted a study at four hospitals from June 2003 to July 2005 to investigate the etiologies of bacterial meningitis in Bangladesh. A total of 2,609 patients met the clinical case definition, and 766 had cerebrospinal fluid tested by at least one of the following methods: latex agglutination, 16S rRNA gene sequencing, or real-time polymerase chain reaction for Neisseria meningitidis A and C, Streptococcus pneumoniae, and Haemophilus influenzae type b (Hib); culture results were noted from patient records. In total, 189 patients (24%) of those tested, representing all age groups, were diagnosed with bacterial meningitis; 136 (18%) had meningococcal, 23 (3%) had pneumococcal, and 25 (3%) had Hib infection. Twenty percent of patients with Hib meningitis (5/25) were > 15 years old. Case-fatality ratios were 10% for N. meningitidis, 22% for S. pneumoniae, and 24% for Hib. Bacterial meningitis from vaccine-preventable pathogens causes significant morbidity and mortality in Bangladesh in adults and children.