The textbook was created in accordance with the Federal State Educational Standard by profession 150709.02 "Welder (electric welding and gas welding)," PM.04 "Fault detection of welds and quality control of welded joints. "Typical defects of welded joints are considered. International coding of defects depending on their type and location in welded joint is described. Impact of defects on operability of welded structures is considered. Widely used in industry destructive and non-destructive methods of detection and identification of defects (internal and surface) are described. Illustrated are the most rational methods for eliminating defects in fusion, electron beam and resistance welding.