We consider the cryogenic fracture behavior of an elastic-plastic material and the energy dissipation associated with crack extension. The results of a fracture toughness test are presented for a forged JJ1 type austenitic stainless steel plate at liquid helium temperature. Temperatures of a compact tension specimen were also measured during straining at 4 K. A two-dimensional finite element analysis was used to interpret the experimental measurements. The elastic-plastic fracture behavior was analyzed using the Dugdale model and the incremental strain theory. In the calculations the material was assumed to be elastic-prefectly plastic and to obey the von Mises criterion with its associated flow rule. The dissipated energy can be calculated from the change in total elastic strain energy of the specimen during crack extension. From the calculated dissipated energy, the associated temperature field near the crack tip was predicted and compared with the measured values. Generally good agreement was found between the computed and the measured values.