Almost invariably, economists have used HIV prevalence rates in models intended to estimate the impact of HIV/AIDS on the economic performance of nations. However, an individual may be HIV positive for lengthy periods with little or no physical impairment. Particularly in environments where little or no medical care is provided before the onset of severe illness, estimates of sickness rates, referred to as AIDS prevalence rates, should be used. In this regard, it should be noted that AIDS prevalence will not be a constant fraction of HIV prevalence. In countries where HIV prevalence rates are climbing (falling), AIDS prevalence will be a smaller (larger) fraction of HIV prevalence. Accounting for this phenomenon is crucial in Sub-Saharan Africa where some countries have experienced prolonged, sometimes dramatic, trends in HIV prevalence. In this paper a model to estimate the impact of HIV/AIDS on economic growth in Sub-Saharan Africa is developed and tested. It is demonstrated that using AIDS prevalence estimates is superior to using HIV prevalence.