The 2007-08 Tanzania HIV and Malaria Indicator Survey (THMIS) included HIV testing of over  15,000 men and women. According to the survey, 5.7% of Tanzanians age 15-49 are HIV-positive.
HIV prevalence is higher among women than men in both urban and rural areas. Urban residents are almost twice as likely as rural residents to be HIV positive.

Women get infected earlier than men. For women,prevalence increases with age until it reaches a peak at age 30-34 (10.4%). The peak for men occurs between ages 35-39 (10.6%).

Tanzania's HIV prevalence has declined slightly in recent years. The current HIV prevalence rate is 5.7%,with 6.6% for women and 4.6% for men. By contrast,the 2003-04 Tanzania HIV Indicator Survey (THIS) found an overall HIV prevalence of 7.0%, with 7.7% for women (6,000 tested) and 6.3% for men (4,900 tested).

These results show a statistically significant decline in HIV prevalence among men but not among women.

HIV prevalence is highest in Iringa (16%), Dar es Salaam, and Morogoro (9% each). Infection rates are lowest in Zanzibar (less than 1%).

Drivers of the epidemic

1. Promiscuous sexual behaviour
2. Intergerational sex
3. Concurrent sexual partners
4. Presence of other sexually transmitted infections such as herpes simplex x 2 virus.
5. Lack of knowledge of HIV transmission

Contextual factors shaping the epidemic in the country

1. Poverty and transactional sex with increasing numbers of commercial sex workers
2. Men's irresponsible sexual behaviour due to cultural patterns of virility
3. Social, economic and political gender inequalities including violence against women
4. Substance abuse such as alcohol consumption
5. Local cultural practices e.g. widow cleansing
6. Mobility in all its forms which leads to separation of spouses and increased establishment of temporary sexual relationships
7. Lack of male circumcision