It is well known that some hydrazone derivatives of both 2-oxobenzoxazoline and 2-oxobenzothiazoline exhibit potent anticonvulsant activity. In order to investigate the effects of structural modifications on the biological properties, 14 new hydrazones of 5-chloro-2(3H)-benzoxazolinone-3-acetyl hydrazide were synthesized. The chemical structures of the synthesized compounds were established by III, H-1-NMR spectral analyses and elementary analyses. The anticonvulsant activities of the title compounds were tested by the penthylenetetrazole induced seizure test. 5-Chloro-2(3H)-benzoxazolinone-3-acetyl-2-(o-methoxy- benzaldehyde)-hydrazone 4d, 5-chloro2(3H)-benzoxazolinone-3-acetyl-2- (o-methybenzaldehyde)-hydrazone 4g, 5-chloro-2(3H)-benzoxazolinone-3- acetyl-2-(p-methylbenzaldehyde)-hydrazone 4h, 5-chloro-2(3H)-benzoxazolinone-3-acetyl-2-(p-nitrobenzaldehyde)-hydrazone 4m, and 5-chloro-2(3H)-benzoxazolinone-3-acetyl-2-(p-dimethylamino- benzaldehyde)-hydrazone 4n were found more active than phenytoin (CAS 57-41-0) in the tests.