Two regioisomer series, 2-(3-ethyl-4(3H)-quinazolinone-2-ylmercaptoacetylhydrazono)-3-alkyl/3-aryl-5-methyl-4-thiazolidinones (12-21) and 2-arylimino-3-(3-ethyl-4(3H)-quinazolinone-2-ylmercaptoacetylamino)-5-methyl-4-thiazolidinones (22-26), were synthesized by the cyclization of 1-(3-ethyl-4(3H)-quinazolinone-2-ylmercaptoacetl)-4-alkyl/aryl thiosemicarbazides (1- 11) with ethyl 2-bromopropionate in the presence of anhydrous sodium acetate in anhydrous ethanolic medium. The structures of 12-26 were confirmed by analytical and spectral data (IR, H-1-NMR and EIMS). Selected members of the thiosemicarbazides and thiazolidinones were subjected to anticonvulsant activity tests by the National Institute of Neurological Disorders and Stroke MD, USA.