Amyloid-enhancing factor (AEF) is a transferable activity that in CBA/J mice reduces the induction time of splenic amyloid deposition to 48 hours. Azocasein, or AgNo3, can induce AEF in the spleen and liver. In the liver several subcellular organelles possess this activity. This is likely due to AEF's adherent properties. AEF is most effective when given by the intravenous route. After intravenous injection, AEF particulates localize to the perifollicular areas of the spleen and Kuppfer cells in the liver. The effects of AEF administration persist for at least 4 weeks. AEF can be solubilized in 4 M glycerol, is not the amyloid A protein, and is not likely to be the serum amyloid P component. The extract can be fractionated by Sepharose 4B column chromatography. The active component is of high molecular weight, and tentative identification by disc electrophoresis has been made.