Root Cause Analysis has become a very popular tool to help find the Root Cause leading to incidents, including serious consequence that resulted from erroneous NDT findings. In this presentation, a structured methodology will be introduced to help us look into the problems, in particular, problems associate with NDT practices. It is important for us to understand that in order to make good and effective use of our NDT techniques, we need to fully understand what happened when someone failed to detect a defect, or found a defect that does not really exists.