Small-punch tests and determination of fracture toughness J IC were conducted at 4 and 77 K on new cryogenic JN1, JJ1 and JK2 austenitic stainless steels, after isothermal aging. Equivalent fracture strain ε qf was determined by measuring the reduction of mickness in the small-punch test specimen. A linear dependence of J IC on ε qf was found in these new materials. Regression analysis of experimental data produced the following linear relation J IC = 1304.1 ε qf + 8.09 [kJm -2]. An analysis of present work relation was pursued on the basis of material properties and evaluation method of J IC. Results showed that the slope value has a strong dependence on material yield strength and J IC evaluation method. This linear relation is useful for the evaluation of fracture toughness J IC, measuring the equivalent fracture strain ε qf by means of small-punch test. Thus it can be useful for assessing the degradation of fracture toughness in small areas such as, the heat-affected zone in welded components.