In large welded structures such as ships, pressure vesseles, etc., the initial imperfections including misalignments and angular distortions are inevitable in course of assembling and welding workmanship. Some of such initial imperfections are liable to produce unexpectedly high local stresses especially due to bending. The authors have investigated experimentally as well as analytically the effect of out-of-plane bending on brittle fracture initiation from a surface flaw, using surface notched plate specimens subjected to eccntric tension specifically designed for the present purpose. As an analytical tool, the approximate elastic analysis of a surface crack developed by J. R. Rice et al. was utilized on its strain basis and the experimental results were discussed in terms of the COD concept. This report gives a proposal on an engineering method to apply the COD concept to the critical assessment of a surface flaw under combined tension and bending on the basis of critical COD data obtained from the conventional COD testings.