A new radical initiator N,N ' -dipropyl, N,N ' -bis(4-methyl benzene sulfonyl) hydrazide (DBSH) has been prepared by condensation of N-chloro and sodium derivatives of N-propyl,4-methyl benzene sulfonamide at room temperature. As a radical initiator DBSH shows interesting properties that, although homolysis of the N-N band takes place around 52.5 degreesC, only very low polymerization yields (similar to1.0 %) are obtained below 100 degreesC. At 100 degreesC, bulk polymerization of methyl methacrylate proceeds rapidly and the reaction is almost quantitative in 2.5 h. This can be attributed to stability of the sulfamidyl radicals to some extent. Radical initiation efficiency of DBSH is about 0.16 and gives high molecular weight of polymers at that temperature. Presence of sulfamidyl groups in polymer chain ends have been confirmed by NMR and elementary analysis.