Tehran University of Medical Sciences Journal of Biostatistics and Epidemiology 2383-4196 7 4 2021 12 15 413 426 Habibollah Esmaily Department of Epidemiology and Biostatistics, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran Rasoul Alimi Department of Public Health, School of Health, Torbat Heydariyeh University of Medical Sciences, Torbat Heydariyeh, Iran Zahra Meshkat Department of Microbiology and Virology, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran Ali Mohammad Hoseinpour General Practioner, Mashhad University of Medical Sciences, Mashhad, Iran Omid Kiani Clinical Research Development Unit of Imam Reza Hospital, Birjand University of Medical Sciences, Birjand, Iran. Fatemeh Khorashadizadeh Department of Epidemiology and Biostatistics, Neyshabur University of Medical Sciences, Neyshabur, Iran. 2021 08 11 2021 09 18 Objectives: Iran is facing a rapid change in the epidemiological pattern of HIV. We examine trends in disease incidence and factors associated with the development of HIV over the last two decades in Iran. Methods: We retrospectively collected data from patients who attended the Behavior Diseases Consultation Center of Mashhad University of Medical Sciences in Iran. Individuals were contributed if they were HIV-positive. We examined baseline factors including demographic, behavioral and clinical characteristics for all participants. Changes in population characteristics were assessed using chi-square test or the Fisher’s exact test. Results: From 1989 to 2014, 584 individuals were eligible for present analysis according to the inclusion criteria. Most patients were men (87%) with most being 36–52 years old, unemployed (58%), married (39.3%), less educated (47.7%) and had a history of imprisonment (83%). The most common modes of HIV transmission were injection drug use (IDU) (51.4%) and IDU along with the sexual relationship (26.5%). These transmission modes varied significantly according to gender (p-value<0.001). Similarly, IDU and sexual relationship were most important transmission modes in males and females, respectively. The incidence rate of HIV through sexual-related modes had a higher proportion than IDU in recent years. Conclusions: In Iran, the pattern of HIV transmission is shifting from unsafe injection drug to unsafe sexual contact for forthcoming years. Also, increasing trend of HIV incidence in women is remarkable. Accordingly, HIV-prevention strategies need to be changed. https://jbe.tums.ac.ir/index.php/jbe/article/view/696