The Cotton Council has been funding our project, for which we intend to identify cotton varieties with efficiency of dry matter production when irrigation is expensive, or relatively inexpensive. The fonner will be achieved by identifying and testing varieties which show little discrimination against l3c assimilation, since it has been shown that this correlates with water-use efficiency. The latter will have both large photosynthetic capacity and large stomatal conductance. We are also investigating the nature of inheritance of water-use efficiency.