Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 7 2 2021 07 04 457 457 Meysam Abshenas Jami School of Public Health, Isfahan University of Medical Sciences, Isfahan, Iran. Mohammadreza Baneshi Modeling in Health Research Center, Institute for Futures Studies in Health, Kerman University of Medical Sciences Kerman, Iran, Faculty of medicine, center for longitudinal and life course research, school of public health, University of Queensland, Herston, Queensland 4006, Australia Maryam Nasirian Infectious Diseases and Tropical Medicine Research Center, Epidemiology and Biostatistics Department, Health School, Isfahan University of Medical Sciences, Isfahan, Iran, Faculty of biostatistics and epidemiology, Isfahan University of medical science, Isfahan, Iran. 2021 03 14 2021 05 15 Background and Objective: Due to the impact of risky behaviors in the community and the need for getting information and planning in this regard, the number of people with high-risk sexual behaviors in Isfahan will be indirectly estimated by the network scale-up method.  Method: In a cross-sectional study conducted in June2018in14districts of Isfahan, a sample of1000 people was recruited by a non-random multistage method and interviewed using a standard questionnaire to identify people with high-risk sexual behavior. Data are analyzed based on a network scale-up method in the STATA application. Results: According to a report by men, the prevalence of male Extra marital sexual relations (N=2437) and relation with paying prostituted women (N=1211), with non-paying prostituted women  (N=298), Homosexuality (N=696) and history of traveling for sexual relations (N =880/100,000); And according to a report by women, the prevalence of female Extra marital sexual relations (N=1386) and Sex Worker women (Monetary) (N=946), Sex Worker women (Non-Monetary) (N=258), and history of travelling for sexual relations (N=13/100,000). In both sexes, the age group of18 to 30years was more at risk for sexual behaviors than other groups  Discussion and Conclusion: It seems that the prevalence of sexual high-risk behaviors in Isfahan is remarkable as the increased prevalence of sexually transmitted diseases, including HIV, but unfortunately, the required training is low in this regard, more attention should be paying to train people to prevent the prevalence of these high-risk sexual behaviors in society. https://jbe.tums.ac.ir/index.php/jbe/article/view/457