Objective: To determine the prevalence, age-group distribution, serotype, and antibiotic susceptibility patterns of invasive Haemophilus influenzae type b (Hib) isolates in Bangladeshi children because data regarding Hib diseases in developing countries are scarce, which has led to delay of the introduction of Hib vaccine in these countries.Methods: Children diagnosed with meningitis (n = 1412) and pneumonia (n = 2434) were enrolled in this surveillance study for Hib invasive diseases.Cerebrospinal fluid (CSF) and blood specimens, and the subsequent isolates, were processed using standard procedures.Results: During 1993 to 2003, 455 H influenzae strains were isolated from patients with meningitis (n = 425) and pneumonia (n = 30), and an additional 68 Hib meningitis cases were detected by latex agglutination (LA) testing.Overall, 35%of pyogenicmeningitis cases were a result of H influenzae, 97.1%of which were Hib.Most (91.4%) cases occurred during the first year of life.Resistance to ampicillin, chloramphenicol, and cotrimoxazole was 32.5%, 21.5%, and 49.2%, respectively.There was a trend toward increasing resistance for all three drugs.Resistance to ampicillin and chloramphenicol was almost universally coexistent and was associated with increased sequelae compared with the patients infected with susceptible strains (31%[23/75] vs 11%[21/183]; P <.001).Conclusion: Hib is the most predominant cause of meningitis in young Bangladeshi children.Resistance to ampicillin and chloramphenicol and the high cost of third-generation cephalosporin highlight the importance of disease prevention through vaccination against Hib. Objective: To determine the prevalence, age-group distribution, serotype, and antibiotic susceptibility patterns of invasive Haemophilus influenzae type b (Hib) isolates in Bangladeshi children because data regarding Hib diseases in developing countries are scarce, which has led to delay of the introduction of Hib vaccine in these countries. Methods: Children diagnosed with meningitis (n = 1412) and pneumonia (n = 2434) were enrolled in this surveillance study for Hib invasive diseases.Cerebrospinal fluid (CSF) and blood specimens, and the subsequent isolates, were processed using standard procedures. Results: During 1993 to 2003, 455 H influenzae strains were isolated from patients with meningitis (n = 425) and pneumonia (n = 30), and an additional 68 Hib meningitis cases were detected by latex agglutination ) testing. Overall, 35% of pyogenicmeningitis cases were a result of H influenzae, 97.1% of which were Hib.Most (91.4%) cases occurred during the first year of life. Resistance to am picillin, chloramphenicol, and cotrimoxazole were 32.5%, 21.5%, and 49.2% respectively. There was a trend toward increasing resistance for all three drugs. Resistance to ampicillin and chloramphenicol was almost universally coexistent and was associated with increased sequelae compared with the patients infected with susceptible strains (31% [23/75] vs 11% [21/183]; P <.001) .Conclusion: Hib is the most predominant cause of meningitis in young Bangladeshi children. Resistance to ampicillin and chloramphenicol and the high cost of third-generation cephalosporin highlight the importance of disease prevention through vaccination against Hib.