Abstract: In a method of flaw classification on and in welds of planar or arcuate plate-shaped workpieces of uniform thickness by means of ultrasonics, the expected flaw areas of the workpiece are pre-examined manually and are then examined systematically using the ultrasound echo image method in separate cross-sectional planes. A B-scan is thus generated, and changing the position of the transducer on the workpiece and/or the transmitting direction enables defects to be located by calculating the delay time of ultrasound waves in the go-and-return directions within the workpiece under consideration of possible reflections at the rear side (8) of the workpiece. For defining the test conditions, part-specific parameters are considered, such as weld type and weld shape (e.g., double-V-weld and bell seam), weld geometry (e.g. seam angle), and part characteristics (e.g.