The International Union of Theoretical and Applied Mechanics (IUTAM) initiated and sponsored an International Symposium on The Mechanical Effects of Welding. was held in Lulea, Sweden, 10-14 June 1991. The intention of the The Symposium Symposium was to gather active scientists in order to assess the current state of the art and future directions. The field of welding is an area which includes a large number of scientific disciplines, such as materials science, solid mechanics, thermal science, and also mechanical engineering design and production engineering. The intention of the Symposium was to cover the direct mechanical effects of welding and their influence on the in-service behaviour of welded structures. The Mechanical Effects of Welding is a very appropriate theme for an IUTAM Symposium. Progress in this field requires close interaction between researchers in several disciplines. This is reflected in the topics covered. The topics of the different sessions were: o Calculations of Temperatures, Strains and Stresses o Residual Stresses and Residual Deformations o Measurements of Residual Strains and Stresses o Effects of Defects and Residual Stresses on Fracture and Fatigue o Effects of Residual Stresses on Creep Deformation o Effects of Residual Deformations and Residual Stresses on Buckling There were 50 participants from 12 countries at the Symposium. The 28 papers presented at the Symposium are collected in this volume. A Scientific Committee, appointed by the Bureau of IUTAM, selected the participants to be invited and the papers to be presented.