The commercial test results on the notch ductility of clad steels are shown in the first report, that the ductility of clad steels are varied with clad ratio and clad arrangement. Clad steels have more ductility as clad ratio increases, and the sandwich type of clad arrangement i, e. stainless. steel is arranged at center, increased ductility of clad steels considerably compared with that of other clad arrangements. The results similar to the first report were also obtained by the Double Tension Brittle Fracture Propagation Test developed by University of Tokyo. From these results, the effect of reduction in thickness of mild steel upon the brittle fracture.propagation seems to exist, depending upon the variation in clad ratio and clad rarangement, so various size of impact tests were carried to evaluate this effect. The following results were obtained : the ductility of single and double clad steels were considerably affected by thickness of mild steel, but the sandwich type of clad steel showed more ductility than expected one due to the reduction in thickness of mild steel.