The application of ultrafiltration technology for drinking water production has shown rapid development from the beginning of the 1990s. There has been a constant cost reduction of this technology over the last ten years allowing evolution (new polymers, new module designs, etc.), and a decrease of the system cost, which is based on the membrane cost per m(2). The ultrafiltration process could be evaluated by other factors, such as footprints, equipment and process reliability, operation and maintenance. Since the first full-scale ultrafiltration plant started 14 years ago, Ondeo, Degremont Co. answered the reduction cost objectives by a constant evolution of its products design. This evolution led to the development of a new product, adapted to large plants, based on an improved standardization of the system (the Ultrazur(R) product) and a new module with a filtration surface area of 125 m(2). The new product, called Ultrazur 450, was industrialized in 1997 and was evaluated through semi-industrial-scale trials performed on the Seine River downstream of Paris in 1999-2000. The Ultrazur((R)) 450 (125 m(2)membrane surface per module) was first applied to the Rouen project, a 24,000 m(3)/d drinking water production plant located in France. Following this success on karstic water, the new product was applied as a polishing treatment at Lorient (production plant capacity: 20,000 m(3)/d) since November 2001 and will be applied at Angers (production plant capacity: 120,000 m(3)/d).