In this study, a three-level Box-Behnken factorial design combined with response surface methodology (RSM) for modeling and optimizing of some operations parameter of Multi-Gravity Separator (MGS) to produce a celestite concentrate was developed. The three significant operational parameters of MGS, which are drum speed, tilt angle and shake amplitude, were varied and the results evaluated with the Box-Behnken factorial design. Second-order response functions were produced for the celestite grad e and recovery of the concentrate. Taking advantage of the quadratic programming, a drum speed of 150 rpm, tilt angle of 6 degrees and shake amplitude of 20 mm have been determined as optimum levels to achieve the maximum SrSO4 concentrate grade of 96.9 1%, whereas the maximum level of grade was 95.69% in the tests conducted or predicted. In the same way, a drum speed of 250 rpm, tilt angle of 2 degrees and shake amplitude of 10 mm has been determined as optimum levels to achieve the maximum recovery of 98.35%, whereas it was 95.83% in the tests conducted or predicted. (C) 2007 Elsevier B.V. All rights reserved.