Bovine acidic and basic fibroblast growth factors (aFGF and bFGF) dose-dependently stimulated the release of nerve growth factor (NGF) in a culture medium of mouse astrocytes. The NGF concentration in the medium started to increase compared to that of the control cultures 4 h later and was further sustained for 24 h when aFGF was contained. The content of NGF mRNA in the astrocytes treated with aFGF peaked at eightfold over the control level after 4 h. The astrocytes did not proliferate until after 72 h when treated with FGFs under the conditions employed. These results indicate that aFGF stimulates the biosynthesis of NGF in cultured astrocytes without promoting cell proliferation.