This research aims to develop a new approach replacing a centrifugal separator with a hydrocyclone in a tapioca Starch production process. The studied hydrocyclone was designed on the basis of Bradley's geometry, which is suitable for starch-water separation according to a small density difference and small diameters of starch particles. Three factors. i.e.. pressure drop across the hydrocyclone (Delta P), feed concentration [C], and apex diameter (D-u), were varied into three levels at 2, 4 and 6 kg/cm(2); 3, 7, and 11% weight by volume; and 1.5, 2.1, and 4.0 mm, respectively. The hydrocyclone's performance indices (i.e., % solid recovery (%R), % split (%R-v), reduced efficiency (E')) and Cut size diameter (d(50)) were determined. The experimental results were used to construct empirical models predicting hydrocyclone efficiencies from the pressure drop, feed concentration. and apex diameter. The models for three indices were: %R = 70.71(Delta P)(0.15) . [C](-0.09) . D-u(0.17), %R-v = 30.69(Delta P)(-0.09) . [C](0) . D-u(0.47), and E' = 54.95(Delta P)(0.31) . [C](-0.17) . D-u(0.19). (C) 2008 Elsevier B.V. All rights reserved.