The general objective of the present work is to study the brittle fracture of the coarse-grain heat-affected zone (CGHAZ) of a C-Mn steel. The target is to develop a probabilistic model for brittle prediction for the CGHAZ based on microstructural data. The model is based on local approach. In order to validate this model, fracture mechanical test specimens (3-point bend) have been tested at different low temperatures; temperature dependence of fracture toughness was obtained. Post-morten examination of the fracture surfaces is used to gather information about the nucleation and arresting abilities of the different phases and interfaces respectively. Metallographic analysis has also been carried out for the HAZ.