Experiments were made to investigate the notch toughness of bead welded high tension steels, WT 50, WT 60 and WT 80. Kinzel bend test and Double Blow impact test were performed to make clear the characteristics of fracture initiation in the heat affected zone of weldments. As the results of experiment, the following were revealed. (1) The bend angle at maximum load was proposed as the most suited criterion to measure the ductility transition in Kinzel bend test. It was shown using this criterion that the weldments were remarkably notch brittle as compared with base plates. (2) Energy for fracture initiation ( W_i , ) vs. temperature curves were measured in Double Blow impact test, and a ductility transition temperature, ( T_rEi ) 2, was determined from these curves. The adverse effect of welding was marked in WT 60 and WT 80, whereas such effect of welding was unexpectedly slight in WT 50.