Ultrafiltration (UF) and diafiltration (DF) of cheddar cheese whey have been carried out after adjusting pH of whey to various levels ranging from 3.0 to 7.2 and imparting different heat treatments in a pilot scale hollow fibre UF plant, possessing PM 50 polysulphone membrane. Concentration has been carried out at 50 degrees C and 1.75 and 0.5 bar inlet and outlet pressures, respectively toe volume reduction of 95% followed by diafiltration in order to elicit their effect on flux and composition of resultant whey protein concentrate (WPC). It is evident from the results that a significantly higher flux could be obtained when whey was processed either at a pH of 3.0 or 7.2 along with a preheat treatment of 80 degrees C/15 s compared to other levels of pH 4.5, 5.6 and 6.4 and heat treatment 60 degrees C/30 min. By UF the protein content on dry matter increased to a level ranging from 61.48 to 63.82% from an initial value of 14.89%. The lactose content decreased to a level ranging from 25.60 to 28.50% from an initial value of 76.14%. Whereas the ash content to a level of 3.17 to 6.23% from 8.20%. The pH of processing had significant effect on ash content being minimum at pH 3.0 (3.17%) and maximum at pH 7.2 (6.30%). The calcium and the phosphorus content of retentate followed the similar pattern as that of ash.