A new method for manufacture of natural cheese was developed using 5X ultrafiltered whole milk retentate. The retentate was prefermented to pH 5.0-5.2 before curd formation to simplify the cheese making process. It was demonstrated that the process can be made commercially feasible. Ultrafiltration and diafiltration of whole milk were done so that the desired level of residual lactose was left in the retentate. Retentate was inoculated with lactic starter culture and incubated (prefermented) until all lactose was converted to lactic acid. The final pH stabilized at about 5.0-5.2; the desired pH of the cheese curd. Incubation at 25°C allowed the retentate to remain liquid during prefermentation and easily pumped through pipes. After prefermentation, retentate was passed through a mechanical curd former where rennet was injected and mixed. The retentate-rennet mixture coagulated as it traveled upward through a cylinder. The curd emerged from the curd former and was cut into cubes by a grid of knives. The curd cubes were treated for removal of moisture by cooking in liquid and evaporation under vacuum. After moisture removal, curd was drained. salted and pressed. Cheddaring and milling were unnecessary. Experiments were performed to determine proper methods for preparing retentate. Diafiltration level was significantly related to lactose concentration in retentate (p=.OOO 1) and final pH of fermented retentate (p=.OOO1). Acidified permeate and acidified, deionized water were evaluated as cooking liquids. Cheese made from curd cooked in permeate had acid defects. but curd cooked in water produced cheese with a pH similar to conventionally produced Cheddar cheese. Moisture content of all finished cheese was excessive for Cheddar cheese. Body and texture of cheese made from curd cooked in water was close to conventionally produced Cheddar cheese. Diafiltration may be used to control final pH of fermented retentate. Prefermentation of retentate prior to cheese making will simplify equipment and shorten manufacturing time. Commercial application of the process is discussed.