The fracture toughening behavior of polystyrene/high density polyethylene blends compatibilized by 10 wt % of a styrene-ethylene-butylene-styrene triblock copolymer (SEBS) was assessed using single-edge notched tension (SENT) and double-edge notched tension (DENT) specimens of various gauge lengths over a wide range of tensile rates. The fracture of DENT and SENT specimens was completely ductile under the plane-stress condition. A linear relationship was observed between the specific total work of fracture and the ligament length (L) for a given L range. The results showed that the essential work (w(e)) was independent of the tensile rate (R) range of 1-30 mm/min, and it then decreased considerably when R was increased to 50 mm/min and above. However, the nonessential work exhibited a rate independent trend behavior. In addition, w(e) and the specific nonessential work of fracture (beta w(P)) were basically independent of the gauge length (G), provided that G was greater than the width of the sample. Finally, it was also shown that the w(e) and beta w(P) values for SENT specimens are obviously greater than those for DENT specimens.