This paper describes the synthesis and pharmacological evaluation of a number evaluation of a number of substituted 1,3,4-thiadiazoles. The first member of the series, 2-(aminomethyl)-5-(2-biphenylyl)-1,3,4-thiadiazole (7) was found to possess potent anticonvulsant properties in rats and mice and compared favorably with the standard anticonvulsant drugs phenytoin, phenobarbital, and carbamazepine in a number of test situations. The potency of compound 7 was maintained on alkylation of the side-chain nitrogen atom; however, aryl substitution or chain lengthening caused a drop in potency. Replacement of the 2-biphenylyl group by phenyl or benzyl also lead to inactive compounds.