We ask whether prime-age adult mortality due to HIV/AIDS decreases the endowment of knowledge for agricultural production in Kagera, Tanzania, reducing total factor productivity. We also quantify how much this negative effect contributes to the decrease in long-term household agricultural output growth compared to the contribution of decreased accumulation of productive assets; household members, land, and livestock. We find that prime-age adult mortality decreases the accumulation of knowledge stock as total factor productivity and the contribution of this negative effect to the decrease in agricultural output growth is larger than the contribution of decreased accumulation of each productive asset.