Most publications on lamellar tearing relate to metallurgical investigations, although some process work has been carried out.At present the designer has to examine the available literature and draw his own conclusions.This report tries to isolate those variables which are important to the welding designer and to explain their relevance in a given situation.It is difficult to adopt a design philosophy for lamellar tearing, when the effect of certain variables cannot be assessed for theoretical and experimental reasons, but the designer must have some evidence as a basis for his decisions.