The behavioral and convulsant effects of cefazolin, a beta-lactam derivative, were studied after intraperitoneal administration to DBA/2 mice, a strain genetically susceptible to sound-induced seizures, and Swiss mice. DBA/2 mice were more susceptible to seizures induced by cefazolin than were Swiss mice. The proconvulsant effects of some quinolones on seizures evoked by intraperitoneal administration of cefazolin were also evaluated in DBA/2 mice. Our study also demonstrated that the order of proconvulsant activity in our epileptic model was pefloxacin > enoxacin > ofloxacin > rufloxacin > norfloxacin > cinoxacin > ciprofloxacin > nalidixic acid. The relationships between the chemical structures and proconvulsant activities of quinolone derivatives were studied. The relationship between lipophilicity and proconvulsant activity was also investigated.