Background Sexual partnership patterns influence risk of STI transmission. We describe the pattern of partnerships reported by youth in a survey in rural Tanzania and calculate the UNAIDS recommended measure of concurrency.

Methods In 2007/8, sexual partnership histories were collected, through a face-to-face questionnaire, from 13,814 15–30 y-olds (90% aged 19–25 y) in 20 communities, in Mwanza, Tanzania. Partnership patterns of sexually active participants were described based on reported dates of first and last intercourse with their last 3 partners in the past year. One-off partnerships had the same date of first and last intercourse. Point prevalence of concurrency was calculated at 6 months prior to the survey.

Results Females and males had mean age of 21 and 22 years respectively. In the year prior to the survey, 87% of females and 79% of males reported at least one sexual partner, and 15% of females and 44% of males reported > 3 partners. Among those reporting 1–3 partners, 47% of one-off partnerships started within 4 months of the survey suggesting reporting bias and/or censoring of data. Only 3% of females reported > 2 new partners in the previous year compared to 26% of males, and 3% of females reported > 1 partner in the last 4 weeks compared to 18% of males. The point prevalence of concurrency was 2.3% for females and 10.7% for males. Partnership patterns varied by sex and marital status (Table). The ‘Previously married’ group were the most likely to report multiple partners.

Conclusions High levels of multiple and concurrent partnerships were reported by males and the ‘previously married’. Further analysis of the characteristics of the specific partners and partnerships will be completed to understand the risk associated with each pattern of partnerships. Analyses will also be adjusted for the bias introduced by restricting questions to the last 3 partners.