Response surface methodology was used to optimize operating conditions of thin layer drying of coroba slices. A rotatable central composite design was used to develop models for the responses. The independent variables were air temperature, air velocity and drying time. The responses were final moisture content, drying rate, energy efficiency and exergy efficiency. The second-order polynomial models with transformed responses were developed from experiment data to generate 3D response surfaces and contour plots. Applying the multiresponse optimization the optimum operating zone was located within the intervals from 89.7 degrees C to 91.2 degrees C, from 64 min to 71 min for air temperature and drying time, respectively, and air velocity fixed at 1.08 m/s. Applying the desirability functions the optimum conditions were temperature equal 90.6 degrees C, drying time equal 69 min and air velocity equal 1.08 m/s. (c) 2007 Elsevier Ltd. All rights reserved.