The book ’’Diversity analysis of soybean for water use efficiency(WUE) using carbon isotope discrimination (CID) technique” has been designed to accommodate the recent development in this rapidly growing subject. This book provides theoretical concepts and practical procedures for appreciation of the imperatives and the practices of WUE using CID technique in soybean. In India soybean mainly cultivated as rainfed crop. Under such condition breeding for increased water use efficiency (WUE) has been shown to be the most potent strategy. Development of CID technique as an alternative for measuring WUE in C3 species has made it possible to measure WUE in a large breeding population. The work needs to be extended in Indian context. The present investigation makes an attempt for the first time in India in soybean to screen a large set of soybean germplasm for WUE using CID technique with the following two specific objectives. First to assess the variability in soybean genotypes with special reference to WUE using CID technique, and second objective were molecular diversity analysis of genotypes showing high and low WUE.