The basic aim of this current research is to reliably detect and size defects in complex geometry welds using the well-known ultrasonic time of flight diffraction (TOFD) technique. A complex geometry weld specimen with various artificial defects was designed and fabricated. Different combinations of probe angles and probe center spacings were used in experiments for determining the optimum one. TOFD models were also developed for sizing the defects and experimentally verified. Copyright © 2009 by ASME.