Bacterial meningitis, an infection associated with leptomeningeal inflammation, can be life-threatening. A thorough history and physical examination are essential to elucidate potential contributing risk factors and to assess the severity of illness. The diagnostic evaluation includes obtaining cerebrospinal fluid for cell count and differential, glucose and protein concentrations, gram stain, and bacterial cultures. Blood and urine cultures should be collected depending on the clinical presentation. A complete blood cell count with differential and serum electrolytes round out the minimal appropriate laboratory work-up for patients suspected to have bacterial meningitis. The common bacterial causes of meningitis differ by age. The most frequent etiologic agents in neonates include Streptococcus agalactiae (Group B streptococcus), Escherichia coli, and other gram-negative enteric rods. Listeria monocytogenes is no longer a common cause of bacterial meningitis in this age group but should still be considered as an uncommon possibility during the initial evaluation of newborns and infants less than 3 months of age. Between the ages of 1 and 3 months, Streptococcus agalactiae, Streptococcus pneumoniae, and Neisseria meningitidis account for most infections. After 3 months of age, invasive infections caused by Streptococcus agalactiae are no longer common. Haemophilus influenzae type b was once the most common cause of bacterial meningitis in children. Presently, cases are only seen in unimmunized children or who are subsequently found to have a serious humoral immune deficiency. The pathogens most identified in children, adolescents, and adults with bacterial meningitis are Streptococcus pneumoniae and Neisseria meningitidis. Beyond age 50 years, Listeria monocytogenes reemerges as an important agent of bacterial meningitis. Empiric antibiotic therapy should be started as soon as feasible, usually immediately after the cerebrospinal fluid is collected. Ampicillin is combined with gentamicin or an extended-spectrum cephalosporin [cefotaxime (where available), ceftazidime, or cefepime] for neonates. An extended-spectrum cephalosporin (ceftriaxone or cefepime) is combined with vancomycin for children, adolescents, and young adults. The regimen used for older adults should also include ampicillin to optimize coverage against Listeria monocytogenes. Empiric therapy should be modified to definitive therapy when the etiologic agent has been identified and antibiotic susceptibility testing results are available. Several recommended antibiotic regimens for treating bacterial meningitis include higher doses administered more frequently than those used for serious infections outside of the central nervous system. Careful attention to recommended antibiotic dosing intervals during empiric and definitive treatment is essential. Even with appropriate early diagnosis, immediate initiation of appropriate antimicrobial treatment, and the availability of expert supportive care, significant morbidities and deaths occur. The prevention of bacterial meningitis is best accomplished by ensuring timely and complete age-appropriate immunizations and through the appropriate use of post-exposure antibiotic prophylaxis for those exposed to individuals with invasive infections caused by either Neisseria meningitidis or Haemophilus influenzae type b.