en Original article Original article <p> <strong> Introduction </strong><strong>: </strong><i>Haemophilus influenzae </i>is a gram-negative bacterium causing a variety of respiratory infections in developing countries, especially in children. Nasopharynx carriers of <i>H. influenzae</i> are the prominent source and transitional vectors of invasive diseases. As very limited information on <i>H. influenzae</i> carriage rate in Iran was available, an evaluation on prevalence of this bacterium in children ≤ <strong>‌ </strong>6 years old seems crucial. <strong>Methods: </strong>Totally 533 mucus samples were collected using nasopharyngeal swabs from children ≤ <strong>‌ </strong>6 years old who lived in 4 nursery centers in Tehran or refereed to the Children's Medical Center of Tehran, Iran, from August 2011 to October 2012. The samples were transported in Stuart transport medium to the Microbiology Laboratory of Pasteur Institute Tehran, Iran, and were cultured on chocolate agar containing bacitracin antibiotic. The initial diagnosis for detection of <i>H. influenzae</i> was performed by standard biochemical tests, and confirmation was achieved by PCR assay targeting outer membrane protein (<i>omp</i>) <i>P6</i> gene. <strong>Results: </strong>Based on primary cultures and biochemical tests, out of 533 samples, 182 (33%) showed to be <i>H. influenzae</i> positive, but PCR assay confirmed presence of <i>H. influenzae</i> in 153 (28%) isolates 56(37%) belonged to girls and 97 (63%) to boys. The prevalence of <i>H. influenzae</i> in three different age groups: ≤ <strong>‌ </strong>24, 25-48, and 49-72 month-old children were 31 (20%), 69 (45%), and 53 (35%), respectively. <strong>Conclusion </strong>: Our results showed a high rate of <i>H. influenzae</i> carriers among children ≤ <strong>‌ </strong>6 years old, which is similar to those of other unvaccinated countries.<i> H. influenzae</i> carriage rate was associated to age and respiratory infection diseases. The children aged 25-48 months showed a higher rate and the rate reduced with increase in age. Further investigation including molecular studies is required to obtain the carriage rate throughout the country. <i>J Med Microbiol Infec Dis, 2014, 1 (2): 5 pages. </i></p> Haemophilus influenzae, Polymerase Chain Reaction, Nasopharynx, Iran 23 27 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-35-1&slc_lang=en&sid=1 Pantea Jalali No Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran Seyed Fazlollah Mousavi Yes Department of Bacteriology & Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran Nima Rezaei No Research Center for Immunodeficiencies, Children's Medical Center, Tehran University of Medical Science, Tehran, Iran