Technical Abstract: Properly controlling the cotton ginning process increases fiber yields and monetary returns to the cotton farmer, improves fiber length distribution, and reduces short fibers, neps, and seed-coat fragments. A computerized process control system that utilizes the cotton market price and the performance characteristics of gin machinery to determine the optimum machinery sequence is now available. Cotton moisture, color, and foreign matter measurements are made with electronic devices at three stations in the gin system and are used to control the gin process. Special routing valves are used to bypass or select any combination of seed cotton cleaners dryers, and lint cleaners. When gin machinery is bypassed, the quantity of marketable lint is increased and the amount of fiber damage is decreased. Ginning characteristics of cotton varieties differ in terms of energy requirements, fiber turnout, and the change in fiber quality. In studies at Stoneville, MS, seed cotton cleaning efficiency ranged from 51% to 72% and lint cleaning efficiency ranged from 48.4% to 66.3% across varieties. Lint turnout ranged from 33.1% to 36.8% and differed from breeders lint percent by 2.9% to 6.8% which suggested unequal response of the varieties to conventional ginning. Several new drying systems are in use that offer some advantages. Spindle-harvested cotton contains 5 to 10% waste. The fibrous component of this waste can be cleaned and marketed advantageously to the gin while the plant parts can be converted to a valuable product by managed composting.