Time-dependent changes in both nerve growth factor (NGF) and acidic fibroblast growth factor (aFGF) levels in the rat brain after cortical cavity lesioning were examined, by using sensitive enzyme immunoassays (EIA) specific for each factor. In the cavity fluid, the NGF level increased rapidly and temporarily with a sharp peak 16 h after lesioning. A relatively high level was sustained during the next 3-6 days. Contrary to NGF, aFGF was first detectable only 10 days after lesioning, and its level increased gradually until 30 days. These results suggest that NGF and aFGF would play some roles for neuronal repair in different ways.