Breaking strength of cotton fiber is an important attribute. A related piece of information that has the same units is the modulus, which indicates the elasticity. Determinations of the breaking strength and modulus of cellulose gives an indication of the idealized ultimate traits of a cellulosic material, to which cotton's properties can be compared. The organization of the cellulose crystallites in cotton fiber will surely diminish the strength and modulus. Models of these levels of organization are critical to understanding the breakage process in fiber, an understanding that could lead to improved fiber properties. The modulus of cellulose can be calculated by stretching molecular models with the computer. The molecule is stretched and the stored potential energy is calculated as the stress. The modulus is the slope of the stress/strain curve. The stress has been calculated with empirical force fields a number of times, with different results. We have undertaken similar calculations with electronic structure theory, also called quantum mechanics. Such calculations have the advantage of being more accurate in principle, as well as being suited to studying breakage. This lecture will show our preliminary results.