Between July 2005 and January 2006 we evaluated 1248 Paraguayan active duty military volunteers. Participants provided a blood sample for HIV testing and answered an anonymous survey. HIV seroprevalence was 0.4% (5 of 1248) among participants. The median age at first sexual intercourse was 16 years. Only 14.8% of participants reported condom use with every sexual encounter. Military students used condoms the most. Participants older than 45 years, compared with younger participants, had a fourfold (adjusted odds ratio 4.3) increased risk of not using condoms. Men were less likely to use a condom, more likely to practice anal intercourse, and had more sexual partners than women. Officers and non-commissioned officers were identified to have a twofold (as measured by adjusted odds ratio = 2.00 and 2.22, respectively) increased risk of having more than two sexual partners in the last month compared with students. Both officers and NCOs were twice as likely as students to practice anal intercourse. Despite the high-risk behaviors reported by those surveyed, HIV seroprevalence in active duty personnel was low. Future efforts should emphasize on the correct condom use keeping focus on the high-risk behaviors of groups at risk, and on routinely testing the military personnel for HIV.