With the epidemic of HIV and AIDS in recent years, attention has focused on the effects on mood and depression. In common with other life-threatening illnesses, positive HIV status and AIDS itself can be involved as factors in provoking depression in their own right. HIV infection also carries with it other potent adverse connotations including a degree of social stigma, the risk of losing other loved ones including partners, and financial problems. It has also become apparent that the HIV virus itself can produce mood changes directly. This virus is known to invade the central nervous system preferentially, and may lead to changes in the brain similar to those found in Alzheimer's disease and other forms of dementia. Even before this stage of the illness, depression may be a feature. There are therefore several ways in which HIV can cause an individual to become depressed and this is likely to remain an important area of research.