The aim of this work was to predict the rejection of aroma compounds and permeate flux during the reverse osmosis concentration of apple juice at laboratory and pilot-plant scales. For the concentration, the MSCB2521 R99 and MSCE 4040 R99 spiral wound membranes (Separem, SpA, B-lella, Italy) were used at laboratory and pilot-plant scales, respectively. The preferential sorption-capillary flow model was considered for the calculations. Experiments were performed at different transmembrane pressures (1.5-7.0 MPa), feed flows (200-600 L/h at laboratory scale and 4200 L/h at pilot-plant scale), temperatures (20-30 degreesC), and concentrations (10.0-22.7 degreesBrix). Good agreement between experimental and estimated data was observed for most of the aroma compounds and operating conditions used. When working at 7,0 MPa transmembrane pressure, 4200 L/h feed flow, and 25 T temperature, concentrations higher than 22 degreesBrix can be reached with high permeate fluxes (higher than 25 Lh/.m(2)) and high aroma retention (higher than 80% for most of the compounds).