A number of nondestructive testing systems are reviewed which can be used to search out and locate all types of weld defects and discontinuities - lack of fusion or bond, cracks, inclusions, undercut, etc. These systems include: visual inspection; radiography, using either X-rays or gamma rays; fluoroscopy; eddy currents; ultrasonics; magnetic particles; and liquid penetrants, using either a visible dye or a fluorescent dye.