Background & aim: Flies are important in the region in terms of mechanical transmission of pathogens, sciatica and forensic entomological research. Identification of species in different regions is the first and most important way to control vector-borne diseases in the region. Therefore, the aim of the present study was to determine the diversity of species and relative abundance of flies of medical importance in Golestan province during 2018-2019. Methods:In the present descriptive study, the samples included medically important flies, which were sampled in both urban and rural areas, including eight stations in Ramyan city in 2018.Trapping was done monthly, on sunny days and on the hottest day of the month. Entomological nets and cone traps were used to catch adult flies. Species identification was performed based on valid keys. The collected data were analyzed using Microsoft Excel software. Results:In the present study, 10 species of Musca domestica (housefly) (53.75), Muscina stabulans (7.26), Lucilia ceasar (14.39), Lucilia sericata (7.91), Calliphora vicina (8.95), Sarcophaga africa (1.55), Sarcophaga aegyptica (0.51), Calliphora vomitoria (3.48), Sarcophaga argyrostoma (0.75), Muscina levida (0.18) in three family including Muscovidae, Sarcophagidae and Acrostida were captured. The most abundance of flies were observed in garbage collection sites and animal places. Musina levida species was reported for the first time from northern Iran in this study. Based on the results of temperature and humidity fluctuations, it was established that the higher temperature and decreasing humidity, the more abundance of flies' population were obsereved. Conclusion:Due to the high abundance of flies in waste collection sites and animal sites, rapid transfer of non-residential areas and their sanitary burial is necessary to reduce the population of flies. It is necessary to move animals out of residential areas and provide health advice to people and health centers on diseases transmitted by flies in the warmer months of the year.