OBJECTIVES Exactly three decades ago first cases of HIV infection and AIDS were described, this within the population of men who have sexual relations with men (MSM). Since then until this day, the MSM population is still a population under heightened risk for HIV infection. The epidemiological characteristics of the MSM are significantly different form other groups under heightened risk of HIV infection. Among the MSM population, there is a population with particularly heightened risk of HIV infection. The aim of this research is to determine which risk factors or a group of characteristics heighten the risk of HIV infection among the MSM population. Aside from this, the MSM population differs from region to region and it is important to determine which key risk factors are conditions for the infection to occur. PATIENTS AND METHODS Respondents are men who have sexual relations with men and were recruited form the general population and among the HIV positive patients. There was a total of 296 respondents. The respondents were questioned anonymously and on a voluntary basis. From the total number of respondents two groups were defined: those MSM found to be of HIV positive status (patient group) and those MSM whose HIV status was negative (control group).The analysis was conducted having in mind epidemiological characteristics such as age, place of birth, education achieved, occupation, stay abroad. Risk behaviors related to HIV infection were described: sexual behavior, sexual orientation, the number of partners, condom use, frequency of anal and oral sexual relations, addictions and other characteristics. A case control study was conducted in which differences among both groups according to relevant epidemiological characteristics were tested. RESULTS This paper confirms the hypothesis that HIV positive MSM indeed differ from the HIV negative MSM, that is, from other MSM population. Firstly, the HIV positive MSM have a significantly higher number of partners (Mann-Whitney U 4483,5, p<0.001). The higher the number of partners, the higher the possibility that the partner is HIV positive and can transmit the infection. HIV positive MSM had sexual relations with persons from abroad significantly more often (OR 2,54, 95% CI 1,34-4,84). Persons who had sexual relations with a foreign citizens are under a 2,36 times higher risk of HIV infection in comparison to those who did not have sexual relations with a foreign citizen. The HIV positive persons more often state having sexually transmitted diseases in history prior to becoming HIV positive, unlike those MSM who are not HIV infected (45,9% : 11,1% that is, OR 6,79, 95% CI 3,49-13,19). The HIV positive MSM are significantly more often infected with hepatitis B (OR 6,58, 95% CI 1,86- 23,30), gonorrhea (OR 3,24, 95% CI 1,13-9,34), syphilis (OR 17,74, 95% CI 3,43- 122,87) and genital herpes (OR18,39, 95% CI 2,03-424,70). Persons with a history of syphilis have 9,35 times a higher chance of getting infected with HIV. The HIV positive MSM have partners of the same (male) sex significantly more often (OR 2,64, 95% CI 1,34 - 5,21). HIV positive MSM use condoms significantly more often at anal sexual intercourse than at oral sexual intercourse (OR 3,59 a 95% CI 1,67-7,79). CONCLUSION The results of this research will be used in future activities targeted towards the MSM population, as a population at a particular risk for HIV infection. A further monitoring of this population is important, as are particular interventions in order to decrease the possibility of HIV infection, and with it, the stigmatization and marginalization of this population.