There is a need to develop cotton ginning methods that better preserve length uniformity, a fiber characteristic that is critical with newer, more efficient air-jet spinning technology. This report summarizes results of harvesting and ginning studies within the past fifteen years that included High Volume Instrument (HVI) fiber length uniformity index (uniformity). The studies concluded that cultivar was an important determining factor and some production practices, such as early defoliation and stripper harvesting, could also reduce uniformity. Uniformity was not adversely affected by seed cotton cleaning machinery (cylinder cleaners and stick machines). Saw ginning reduced uniformity more than did roller ginning, from 0.8 to 2.0%. Uniformity was negatively affected by the saw-type lint cleaner, from 0.4 to 1.1% per stage. Moisture restoration before lint cleaning partially mitigated (0.5%) lint cleaning’s decrease in uniformity. Studies reviewed in this report suggest that most of the decrease in uniformity occurs at the saw-type lint cleaner feed bar. Although uniformity was not affected by lint cleaner grid bars, faster lint cleaner saw cylinder speeds did reduce uniformity. Roller gin-type lint cleaners reduced uniformity 0.2 to 0.8%, which was less than the reduction caused by saw-type lint cleaners.