Basic fibroblast growth factor (bFGF) has been shown to have neuroprotective effects in animal models of ischemia. To determine whether bFGF is protective against seizure-induced brain damage, we administered bFGF through osmotic pumps prior to, and after treatment with kainic acid (KA). Recombinant bFGF, CS23, a modified human bFGF, was infused into the lateral ventricles in rats for 2 days before and 5 days after the injection of KA. Control rats received equal volumes of phosphated saline over the same period of time. Infusion of 5 micrograms/ml of bFGF (0.5 microliter/h) did not modify the latency and duration of seizures induced by intraperitoneal injections of KA. However, bFGF prevented cell loss in the hippocampus in 80% of the rats. In control rats, cell loss in the hippocampus was found in all rats. These results indicate that bFGF has a substantial neuroprotective effect.