Most people living with AIDS in sub-Saharan Africa have had neither a biomedical diagnosis nor antiretroviral medication, leading to the question of how individuals understand and treat AIDS. This study examined general illness, sexually-transmitted infection (STI) and AIDS treatment-seeking behaviour in rural Mwanza, Tanzania. From 1999-2002, participant observation was carried out in nine villages for a total of 158 person-weeks. Treatments were pluralistic and opportunistic, usually beginning with home remedies (western or traditional), followed by visits to traditional healers (THs) and/or health facilities (HFs). THs were sometimes preferred over HFs because of familiarity, trust, accessibility, expense, payment plans, and the perceived cause, nature and severity of the illness, e.g. only THs were believed to successfully treat bewitchment. Some people, particularly young girls, delayed or avoided seeking treatment for STIs for fear of stigma. Most STIs were attributed to natural causes, but AIDS was sometimes attributed to witchcraft. Locally available biomedical care of people with AIDS-like symptoms consisted of basic treatment of opportunistic infections. Most such individuals repeatedly visited THs and HFs, but many stopped attending HFs because they came to believe they could not be cured there. Some THs claimed to cure witchcraft-induced, AIDS-like illnesses. There is an urgent need for improved biomedical services, and TH interventions could be important in future HIV/AIDS education and care.