In the pharmaceuticals water production process, the UF method is an effective way to remove pyrogen as well as the distillation and RO method. The UF module used for the production of WFI should have such properties as (1) Reliable bacteria and pyrogen removal (2) Biological safety (3) Excellent heat resistance (4) Excellent chemical compatibility (5) Sanitary structure (6) High water flux. Microza® UF “VIP-3017” module has been widely used, and is especially so steam sterilizable that the UF system incorporated with the UF modules is more reliable for this application. When the UF method is applied to the production of pharmaceuticals water including WFI, periodical analysis of UF permeate should be implemented to ensure the quality as the pharmaceuticals water and furthermore air leak test of the UF module should be performed from time to time. During the facility shutdown and steam sterilization of the UF system, a careful attention for the UF system operation should be paid in order to prevent from bacterial contamination at the UF permeate side. The UF method has been already approved in the JP for the production of WFI but is approved neither in the USP nor EP. It is desirable that enough information including data on this application in Japan is submitted to the USP and EP for international harmonization of pharmacopia.