A single specimen fracture-test method for determining the fracture energy of highly deformable materials is presented. This test method is based on the locus method, which determines the critical J- integral value ( J c ) by partitioning the essential energy for crack propagation from the total absorbed energy. The locus method uses the locus of crack initiation points on the load-displacement record of specimens which differ only in initial crack size. With a proper specimen shape and loading condition, the locus line is predictable. When the locus line is predictable J c can be evaluated from a single specimen. Experimental results show that the fracture energy determined by the single specimen method agrees well with those by the tearing energy approach and multiple specimen locus method.