The fluid used in dialysis therapy, hemodialysis, hemofiltration, and peritoneal dialysis consistsof water, electrolytes, buffer and in most cases glucose. Assurance of adequate water quality isone of the most important aspects of ensuring a safe and effective delivery of the dialysistherapy. The water to be used for the preparation of dialysis fluid needs treatment to achievethe required quality. The source of dialysis water is drinking water which is submitted topurification steps that may include various components such as softeners, carbon filters,pressure driven processes such as Reverse Osmosis (RO), deionization units, ultrafilters andmicrofilters. In a RO-system the feed water is pressurized by a pump and forced through theRO membrane to overcome the osmotic pressure. The RO membrane is a semipermeablemembrane that lets water pass through the membrane while retaining impurities from the water,as salt, inorganic molecules, and organic molecules, including microorganisms and bacterialendotoxins, creating a purified product stream. The RO membrane is retaining the impuritiesto different degrees. The purified product water is used by the dialysis machines to give thepatients a safe treatment. The availability of methods to measure the integrity of RO systemsreadily and accurately will aid in making sure water of consistently high quality is deliveredduring the dialysis treatment.In this diploma work, continuous online monitoring, and offline periodic testing of the integrityof the RO membranes were done using conductivity measurement. Samples from product,reject and feed water were collected for offline testing of the conductivity. Other techniquesfor testing the integrity of the RO membrane used were, challenge of the RO membrane withRhodamine-WT, metal analysis by ICP-MS of selected ions and analysis of the concentrationof bacteria. Rhodamine-WT was used as challenge test and is considered as a virus equivalent.Rhodamine -WT is a dye where the fluorescence is measured with a fluorometer. The microbialanalysis was performed by culturing on R2A agar plates.It was observed that the continuous conductivity monitoring, at the time of sample collection,was approximately equal to conductivity values measured offline for the sample collected.Since conductivity measures electric current from dissolved salts and inorganic chemicals,therefore the conductivity measure can be said to be the direct correlation to the present of saltsand not bacteria in the water. The online conductivity monitoring cannot be concluded to beenough to monitor the RO membrane bacterial rejection. Thus, the online continuousconductivity monitoring cannot be used as a continuous online monitoring method formicroorganisms, though the conductivity measured seems to correlate with the number ofbacteria counts in the results.