The role of Kingella kingae as an invasive pathogen of young children is being increasingly recognized, but the niche of the organism in the respiratory tract and its prevalence in the normal flora of children remain unknown. To investigate these two aspects throat and nasopharyngeal cultures were obtained every 2 weeks from two cohorts of children, ages 6 to 42 months on enrollment, attending a day-care center in southern Israel. To determine the age-related prevalence of K. kingae, throat cultures were obtained from children ages 6 months to 14 years hospitalized for elective surgery who had not received antibiotics during the previous 30 days and from healthy infants younger than 6 months attending a well-baby-care clinic for routine vaccinations. During an 11-month follow-up 109 of 624 (27.5%) throat cultures but none of the nasopharyngeal cultures obtained from 48 day-care center attendees grew K. kingae. The monthly prevalence of K. kingae ranged from 6.1 to 34.6% with December and April peaks. Overall 35 of 48 (72.9%) children had at least one positive culture for the organism. Among the 27 children who had > or = 2 positive cultures, continuous and intermittent patterns of carriage were observed. None of the colonized children experienced an invasive K. kingae infection. The prevalence of pharyngeal carriage among surgical patients was 8.0%, and the organism was not isolated from any of the infants younger than 6 months attending the well-baby-care clinic.