The 3-(4-chlorophenyl)amino-4-(4-chlorophenyl)-5-(N-4 chlorophenylthiocarbamido)-1,2,4_thiadiazole possesses significant anticonvulsant activity, devoid of side effect, sedation.Hydantoins and related cyclic ureids have served as an important source in the search for new anticonvulsants. 1 The sulfonyl analogues of Phenytoin, i.e., 1,2,5-thiadiazoles have been reported as potent anticonvulsants. 2 Recently, we have reported the synthesis anticonvulsant activities and related biological properties of 1,2,4 thiadiazoles. 3,4,5,6,7,g 1,2,4-thiadiazoles could be considered bioisosterically equivalent to earlier reported 1,3,4-thiadiazoles 9 and 1,2,5_thiadiazoles2 The anticonvulsant properties observed for 1,2,5-thiadiazoles provided the impetus for the delineation of many of the structural parameters necessary for anticonvulsant activity within this class of compounds. In view of this, and in continuation with our investigations on 1,2,4_thiadiazole derivatives, we describe here the synthesis of some substituted dercvatives of 1,2,4-thiadiazoles and screening them for the jdentification of anticonvulsant activity. It was also the aim to test for sedation. which is chronic side effect in most anticonvulsants. Anticonvulsant profile of synthesized compounds are compared with the standard drugs phenytoin. In our earlier reports 4,597 the parachlorophenyl group attached to amino nitrogen at 3 and directly to nitrogen at 4 positions of the thiadiazole ring have produced the compounds with moderate anticonvulsant activity, Hence, it was proposed to introduce the parachlorophenyl group to the imino njtrogen at 5 position of the thiadiazole ring, in an adduct form in order to observe a compound with enhanced activity. Various substituents were planned to be introduced into the two aryl rings of amino nitrogen at 3 and nitrogen at 4 positions of thiadiazole ring. The synthesis leading to the title compound (l-10) is depicted in SCHEME. The 4-aryl-3-arylamino-5-imino-1,2,4-thiadiazoles on condensation with 4-chlorophenylisothiocyanate forms 1:l adduct, i.e., 3-;;ylamino-4-aryl-5-(N-4-chlorophenyl thiocarbamido)-1,2,4-thiadiazoles. The 4-arylamino-3-aryl-5-imino-1,2,4_thiadiazoles were prepared by the method described in literature.