The steam distillation of Cymbapogon citratus was optimized according to a complete factorial design 2(3). Eight triplicate experiments carried out, with a suitable choice of 3 variables, led to a mathematical model in the form of a first degree polynomial. After effect analysis, one notes that the most important factor (in absolute value) is the water loss of the vegetable material with a negative effect (-0,6); the second is division factor of the plant material with a positive effect (+ 0,4); flow condensation has a negligible effect on the process (-0,125). Interaction factors are also negligible, generally about 0,2 units. The average essential oil volume recovered from 250 g of plant material is 2,1 ml. (C) 2004 Elsevier Ltd. All rights reserved.