Fracture toughness testing of irradiated or aged materials is often limited due to the lack of available material. Subsize Charpy, small CT specimens or small punch test is generally used to overcome this limitation. In this paper, a method based on small notched tensile specimen testing is presented and used for evaluation of fracture toughness properties of a C-Mn steel with a large inclusions content. Specimens are cut in the radial and circumferential directions from a C-Mn steel pipe and tested at 100°C. The diameter of the smallest specimens is 3.6 mm. The average strain at fracture and finite elements simulation of the notched specimens are used to determine the critical values of a local ductile fracture criterion. These values are subsequently used in conjunction with finite element simulations to predict the fracture toughness of the material in different orientations. The predictions are compared with fracture toughness measured on ½ T, 1 T and 2 T-CT specimens.