International Journal of Preventive Medicine (Int J Prev Med)2008-78023720111018308308ENMSc Epidemiology, Kerman Physiology Research Center (Kprc) Kerman University of Medical Science(KUMS).Kerman, Iran.Biostatistics and Epidemiology Department, Kerman University of Medical Sciences, Kerman, Iran.Research Center for Modeling in Health, Kerman University of Medical Sciences (KMU), Iran.201108142011101620111016<p><strong>Objective: </strong>To estimate the size of groups at high risk of HIV, Network Scale UP (NSU), an indirect method, was used.</p> <p><strong>Methods: </strong>500 Kermanian male aged 18 to 45 were recruited. 8 groups at high risk of HIV were defined: Users of opium, unknown drug, ecstasy, and alcohol; intra‑venous drug users (IDUs; males who have extra‑marital sex with females (MSF); male who have sex with female sex workers (MFSW); and male who have sex with other male (MSMs). We asked respondents whether they know anybody (probability method), and if yes, how many people (frequency method) in our target groups.</p> <p><strong>Results: </strong>Estimates derived in the probability method were higher than the frequency method. Based on the probability method, 13.7% (95% CI: 11.3%, 16.1%) of males used alcohol at least once in last year; the corresponding percent for opium was 13.1% (95% CI: 10.9%, 15.3%). In addition, 12% has extra‑marital sex in last year (95% CI: 10%, 14%); while 7% (95% CI: 5.8%, 8.2%) had sex with a female sex worker.</p> <strong>Conclusion: </strong>We showed that drug use is more common among young and mid‑age males; although their sexual contacts were also considerable. These percentages show that special preventive program is needed to control an HIV transmission. Estimates derived from probability method were comparable with data from external sources. The underestimation in frequency method might be due to the fact that respondents are not aware of sensitive characteristics of all those in their network and underreporting is likely to occur.http://ijpm.mui.ac.ir/index.php/ijpm/article/view/308http://ijpm.mui.ac.ir/index.php/ijpm/article/download/308/593