Alzheimer's disease (AD) and its hallmark, plaques, may be due to an imbalance of trophic support. It has been suggested that plaque biogenesis may involve a growth factor which induces sprouting of neurites to form plaques. Thus, we studied the distribution of basic fibroblast growth factor (bFGF), in the hippocampus from AD brain and in rodent brain after entorhinal ablation. Both cases have a partial deafferentation of the hippocampus. The strongest bFGF immunoreactivity in AD was shown in plaques of the dentate gyrus. Rodent brains showed a lesion-induced increase of bFGF in the dentate gyrus, primarily localized to astrocytes. Our results indicate that bFGF may serve an important biological function in plaques and possibly attract neurites.