HIV in Australia was first diagnosed in NSW in the early 1980s, and has had a significant effect on public health. The NSW Government commenced its investment in HIV/AIDS in 1984 and the investment now encompasses research, primary and secondary prevention, and care, treatment and support for people living with HIV/AIDS. A recent study examined the historical impact of the HIV/AIDS epidemic and projected its future impact in NSW. The analysis indicates that the NSW HIV/AIDS investment program has been highly effective in reducing HIV transmission, and has also been cost effective in: avoiding future health-care costs; life years saved; and quality of life benefits. The analysis also indicates that any scaling back of prevention initiatives would result in an increase in the number of people living with HIV.