This study investigates whether HIV prevalence rates impact TFP growth. We construct a panel of data on general macroeconomic indicators and HIV prevalence rates for over 100 countries, for the years 1994 through 2002, and estimate the impact of HIV on TFP growth rates for each country. We find that HIV can have a large negative impact on factor productivity growth in Southern African countries. For example, factor productivity growth in Lesotho falls by up to 23%, and for South Africa factor productivity growth falls by up to 15%. We then investigate the potential impact of the disease on the economic growth of Lesotho and South Africa. This is accomplished by calibrating a single sector, neoclassical model of economic growth with endogenous savings to the two countries. The models show that TFP effects can have large, negative impacts on both per capital and aggregate GDP.