Recent advances in the understanding of the role of surface stress for surface reconstruction, self-assembled pattern formation, alloying, shape and structural transitions, and adsorbate-induced stress are discussed. An understanding of the implications of surface stress requires a thorough theoretical investigation of the relevant processes on the atomic and mesoscale. Progress in the theoretical description of surface stress of clean and adsorbate-covered surfaces is described. A presentation of an optical deflection technique for stress measurements concludes the article.