Scatter of fracture toughness of welds is significantly large due to intrinsic nature of cleavage fracture and stochastic nature of fatigue-crack sampling of a local brittle zone. Under such circumstance, it is often desired to predict a distribution of fracture toughness of the local brittle zone, only. The present paper proposes a method of predicting critical CTOD distribution of a specific microstructure, e.g. coarse-grained HAZ, from weld HAZ CTOD tests. The method is based on the weakest-link assumption and uses a likelihood function which is defined by considering critical CTOD values, as well as crack initiation sites. The proposed method was examined by Monte-Carlo simulations.