The present paper provides a summary of an inter-laboratory round robin on the fracture toughness testing and Master Curve application on unirradiated materials. First, a validation exercise was performed on the analysis of a given forcedisplacement curve. Then, a validation exercise was performed on the application of the Master Curve procedure on a given data set of fracture toughness results. Finally, the preliminary results of the Master Curve application on mini compact tension (MC(T)) specimens by 13 different labs on six different materials (four base materials and two welds) are presented. The validation exercise on fracture toughness data evaluation showed the need for a uniform conversion from front face displacement to load line displacement. The validation exercise on application of the Master Curve approach to obtain the reference temperature proved the equivalence between the T0TEM software and in-house developed softwares. The interlaboratory round robin showed the equivalence between T0 obtained by MC(T) and larger specimens, except for A533B JRQ and 73W. The reasons for the deviations of A533B JRQ and 73W are under investigation. As a general comment, it can be stated that the results from MC(T) specimens often indicate material inhomogeneity as compared to the result from larger specimens. This is likely the consequence of the small sampling volume of the MC(T) specimens.