Flu caused by influenza viruses, is a serious public health problem all over the world with its high morbidity and mortality. Therefore World Health Organization (WHO) regularly collects the results of national influenza surveillance, evaluates the results and shares them on international portal. Thus, it provides the possibility of rapid prevention and preparation of countries that needs to be taken on the fight against the epidemic flu. Starting from 2004-2005 season until today the current flu activity in our country is also followed in accordance with sentinel surveillance. The aim of this study was to evaluate the results of sentinel surveillance data obtained by National Influenza Reference Laboratory in Istanbul University Faculty of Medicine, in 2013-2014 and 2014-2015 seasons. For this purpose, nasal/nasopharyngeal swab samples taken from the patients diagnosed as influenza-like illness by the volunteer family physicians in Izmir, Istanbul, Antalya, Edirne and Bursa were included in the study. A total of 1240 samples were delivered to our laboratory in three days, in Virocult (R) transport culture medium according to cold chain rules. All the samples were studied by real-time polymerase chain reaction (Rt-PCR) according to the protocols of Centers for Disease Control and Prevention (CDC). In our study, the positivity rates of influenza viruses in 2013-2014 and 2014-2015 seasons were detected as 31.4% (202/641) and 44.4% (289/650), respectively. In 2013-2014 season, influenza A(H3N2) virus was the predominant type with a rate of 93.1% (188/202), and the rest was influenza B virus (14/202; 6.9%). In 2014-2015 season, influenza B virus has been dominated with a rate of 60.2% (174/289), and the rates of influenza A(H1N1) pdm09 and influenza A(H3N2) were 30.4% (88/289) and 9.3% (27/289), respectively. The flu season in 2013-2014 has started at 48th week and peaked at 52nd week, while it was started later in the second week in 2014-2015 season and peaked at 10th-13th week. The lineage of the influenza B viruses isolated in both seasons were identified as B/Yamagata. Antigenic characterization of influenza A viruses isolated in our laboratory was found compatible with the vaccine strains. In conclusion, surveillance studies are highly important for the determination of the effects of flu on public health and identification of the approaches for fighting with flu. In this sense, influenza surveillance of the countries are required to implement more effectively in an expanded field of scale.