This paper examines two key dimensions of HIV and AIDS in sub-Saharan Africa, namely poverty and gender, within the particular context of informal settlements. The study, conducted in five informal settlements of Nairobi, Kenya explored the challenges facing women living with HIV and AIDS (WLWA) in informal settlements in Nairobi in terms of the specific risk environments of informal settlements, the support they receive and their perceptions of their future. The data were gathered through an interviewer-based questionnaire administered to 390 WLWA and 20 key informant interviews with Kenya Network of Women with AIDS (KENWA) project personnel. The results show that for WLWA in informal settlements, poverty and poor living conditions combine to increase the risk environment for HIV infection and other opportunistic infections and that the WLWA then face HIV- and AIDS-related problems that are exacerbated by poverty and by the poor living environments. In response, the WLWA had devised coping strategies that were largely centred on survival, including commercial sex work and the sale of illicit liquor, thus increasing their susceptibility to re-infections. Insecurity in informal settlements curtailed their participation in income generating activities (IGAs) and increased their risk of rape and HIV re-infection. Recognising the disadvantaged position of communities in informal settlements, the non-governmental organizations (NGOs), community-based organizations (CBOs) and faith-based organizations (FBOs) provide a range of services including HIV and AIDS information and therapy. Paradoxically, living in urban informal settlements was found to increase WLWA's access to HIV and AIDS prevention and treatment services through NGOs and social networks that are not found in more established residential areas. The sustainability of these services is, however, questioned, given the lack of local resources, weak state support and high donor dependency. We suggest that the economic and tenure insecurity found among WLWA demands in response consistent support through comprehensive, sustainable HIV and AIDS services complemented by social networks and community sensitisation against stigma and discrimination. Fundamentally, the upgrading of informal settlements would address the wider risk environments that exacerbate the poor health of the WLWA who line in them.