Partnership mixing on age group, race/ethnicity, and military status each showed statistically significant difference by partnership type (MSM, MSW, WSM, WSW) (p<0.001). Recent STI was not associated with disassortative mixing on age group or military status but was associated with disassortative mixing on race/ethnicity (p=0.003). 194 of 669 (29.0%) subjects reported concurrent partnerships or suspected sexual concurrency by their partner(s). Suspected sexual concurrency by respondents' partner(s) significantly increased the odds of STI in the respondent after adjusting for partnership type (p=0.02).Military service includes unique social and cultural constructs that may influence sexual partnership formation. While not likely representative of the U.S. military as a whole, these results attempt to identify partnership characteristics and risk factors that may support the maintenance of high rates of select STIs among military populations.