We sought to assess the effect of day care center (DCC) attendance and parental health care work environment on the prevalence of Haemophilus influenzae type b (Hib) pharyngeal colonization in children in Turkey. Children of health care workers were evaluated by nasopharyngeal culture specimens obtained prior to enrollment at a hospital-based DCC at Cerrahpasa Medical Faculty (CMF-DCC) and then again after 3 months of attendance. A larger cohort from this same DCC was evaluated after 6 months of attendance and compared to a group of children of non-health care workers enrolled in Bahcelievler-DCC. As is standard of care in Turkey, none of these children had received the Hib vaccine. Fifty children of health care workers were evaluated prior to their enrollment and then again after 3 months at CMF-DCC. The incidence of Hib carrier state at enrollment was 4% and increased to 22% after 3 months at the DCC. To assess the affect of parental health care employment on Hib carriage rates, 103 children from CMF-DCC and 40 children of non-medical families at Bahcelievler-DCC were evaluated. Hib carrier state was identified in 40.7 and 47.5% after more than 6 months of attendance at CMF-DCC and Bahcelievler-DCC, respectively. No significant difference was observed between carriage rates of children coming from medical and non-medical families and the average carriage rate was 42.6% when duration of day-care attendance exceeded 6 months. Our results demonstrate that Hib carriage rates are affected by the duration of DCC attendance. Parents' employment in a health care facility does not affect carriage rates.