Significant small variations exist in the proportion of the heavy isotope (¹³C) in organic and inorganic materials. The amounts of variations depend on the discrimination against or (in favor of) the heavy isotope through equilibrium reactions or kinetic processes particularly during CO₂ fixation in plants. These variations have also paved the way to measure carbon isotope discrimination in plant materials as a surrogate for water-use efficiency. Thus looking for variation and understanding the inheritance of this character is a prerequisite for improving wheat genotypes showing high water use efficiency and tolerance to drought. The main objectives of this review is to provide an overview of various aspects in which inheritance of Δ is documented and of variation for carbon isotope discrimination reported in wheat under different circumstances. The relationship between carbon isotope discrimination and drought tolerance is also discussed exclusively in wheat.