Residual stresses in welded joints are a consequence of hindered shrinkage of the heated zones and in materials like steels where phase transformations occur of the combined effect of hindered volume expansion. With these two elementary processes any residual stress distribution can be described conclusively if the cooling conditions and the material properties like the transformation behaviour are known. The grade of restraint of the weld seam is the most important boundary condition which is responsible for the opportunity that high residual stresses may occur. The grade of restraint is given by the ratio between the heated zones and the apparent colder material and is not primarily depending on the size of a component. Every way to reduce the grade of restraint offers principally the possibility of an increasing distortion. Many experiments show, that a certain control of the welding parameters which should be carefully adjusted on the properties of each material enables a combination of favourable strength and toughness properties with acceptable residual stresses.