The evaluation of the optimum conditions for concentration of the sweet orange essential oil by wiped film evaporator required a planning of experiments. The factors of the selected centered composite plan are the rate of feed. the temperature of the heated fluid and the stirring velocity. The quadratic model obtained required complementary work by simplex method to determine the optimum. The analysis by gas chromatography of the samples revealed a 18.2 times concentrated oxygenated compound in the residue. (C) 2004 Elsevier Ltd. All rights reserved.