This article concerns the problems encountered in repairing mud brick walls with new adobe. The basic requirements of an adequate approach are first to appreciate the working characteristics of a soil wall, second to know the processes by which the wall decays, and, finally, to be versed in the geotechnical, physical, and chemical behavior of the old and new soils. The main contribution of the article is a list of practical guidelines for repairing adobe walls, with particular emphasis placed on becoming familiar with local adobe building practices.