Industrial production of acid caseins, coprecipitates, and whey proteins is described through flow diagrams and discussion of important operating variables. Variables in continuous casein manufacture include type of acid, pH, precipitation temperature, heating temperature and time, and washing techniques. Precipitation, ultrafiltration, gel filtration, and electrodialysis have been developed to commercial scale for whey fractionation. Ultrafiltration variables include membrane area and geometry, static pressure, flow rate, feed composition, temperature, pH, and membrane characteristics. Performance of gel filtration depends upon bed volume and geometry, feed composition, feed volume per cycle, wash volume per cycle, temperature, flow rates, pH, and gel properties. Electrodialysis is affected by membrane area and geometry, electrical potential, feed composition, flow rates, temperature, membrane characteristics, and brine stream. Recent developments and review literature are discussed.