The present study was performed to evaluate whether the application of Fenbufen is reasonable for predicting the convulsive liability of the quinolone derivatives and to examine whether pentylenetetrazole (PTZ) can be used as a screening tool for their Central Nervous System (CNS) toxic pontential. The convulsive activity of the quinolones was markedly potentiated by the pretreatment of Fenbufen. In combination with Fenbufen, enoxacin (ENX), norfloxacin (XFLX), and ciprofloxacin (CPFX) provoked convlusions and subsequent death at the intravenous doses of 0.5mg/kg, 10mg/kg, and 40mg/kg, respectively, whereas ofloxacin (OFLX) and pefloxacin (PFLX) did not induce convulsions and death even at a relatively high dose of 100mg/kg iv.