We investigated the frequency of pertussis among children in the İstanbul Faculty of Medicine Hospital during a period of four years. Clinical specimens were obtained from children who exhibited symptoms of whooping cough; a portion of the cases were confirmed microbiologically by PCR as pertussis. A total of 410 nasopharyngeal aspirates were taken for detection of Bordetella pertussis/parapertussis. The age groups of the patients were 0-4 months (n=201), >4 -12 months (n=49), 1-4 years (n=79), 5-9 years (n=46), 10-14 years (n=27) and >15 years (n=8). 106 (26%) of all samples were positive for B. pertussis/parapertussis by the PCR method. The Bordetella PCR positivity rates were 36% in 2010, 29% in 2011, 15% in 2012 and 15% in 2013. Due to administration of the DTaP-IPV vaccination at seven years of age starting in 2010, pertussis was not detected in the 5-9 age group after that year. According to this result, the five doses of pertussis vaccination administered as the national vaccine scheme are effective in protecting against the infection. A booster dose for adolescents at 14 years of age as well as a cocoon strategy might also be considered in our country.