Bacterial meningitis is a serious health problem worldwide and little is known about the influence of sex and gender on this disease. In this thesis, we investigated differences between sexes in the aetiology, epidemiology, clinical features, and prognosis of community-acquired bacterial meningitis, analysed sex-based disparities in treatment response, and examined the role of inflammation and sex hormones. First, we gave an overview of sex and gender differences in bacterial infections. We then focused on bacterial meningitis and examined sex-based differences in clinical features, causative pathogens, disease severity, and outcome in adults with community-acquired bacterial meningitis in a prospective cohort study in the Netherlands. We found women to have higher serum inflammatory markers, whereas male sex was an independent predictor of poor prognosis. Using the same cohort, we compared pneumococcal serotype distribution and incidence trends in men and women with pneumococcal meningitis following the implementation of paediatric conjugate vaccines and found no differences in serotype distribution or evidence of serotype replacement in either sex. To investigate whether sex influences the response to anti-inflammatory treatment, we performed a post hoc analysis of a trial of dexamethasone vs placebo and found women to have a greater magnitude of treatment effect, although there was no significant effect modification. Finally, we examined the association between cerebrospinal fluid levels of sex hormones and inflammatory markers, disease severity, and outcome in pneumococcal meningitis. Higher oestradiol levels were associated with an unfavourable outcome and serum and CSF inflammatory markers, whereas higher testosterone was associated with greater illness severity.