To identify more potent anticonvulsant agents and to gain insights into the structural properties determining the potency of a new class of anticonvulsants, some 3a-substituted tetrahydropyrrolo[2,1-b]benzothiazol-1-ones (1a-d) and the thiazole and oxazole analogues (2a-c and 3a-c, respectively) have been synthesized and tested for anticonvulsantactivity against isoniazid-induced seizures in rodents