Book excerpt: Salt-affected soils such as saline or sodic soils are distributed in all continents at various levels of problem intensity. They are soils with high amounts of soluble salts and/or sodium ions. An updated information of their distribution and drivers is a first step towards their sustainable management. This book provides technical guidelines and approach for developing a harmonized multiscale soil information of salt-affected soils. The book is organized into three sections covering seven chapters. The sections are sequentially arranged but independently designed to benefit focused readership who may want to go straight to any section. Section 1 gives the background information. It has three chapters covering existing literature on the characteristics and mapping methods for salt problems in the soil. It is intended to illustrate the basic concepts, linkage of the characteristics of salt-affected soils with input data requirements for their mapping, existing classification methods, and global distribution of these soils. Section 2 covers the methodological procedures for developing multiscale spatial information of salt-affected soils. It has two chapters describing requirements, input data preparation, and the procedural steps for developing spatial information of salt-affected soils. It outlines how data from different sources and characteristics are harmonized and integrated to produce information of salt-affected soils. Section 3 covers information sharing and resources mobilization when developing information on salt-affected soils. It gives the guidelines for preparing spatial maps and steps for value-addition to benefit end-users of the information. It also contains a generic training program for building technical capacity for mapping salt-affected