Drying of olive pomace was studied at 60, 70, 80 degrees C and constant air velocity of 1.5 m/s for various sample thickness and particle sizes. Drying of olive pomace took place in the falling rate period at all temperatures. Drying time changed from 140 to 65 min for 80 degrees C, 170 to 80 min for 70 degrees C and 240 to 125 min for 60 degrees C by changing thickness from 12 to 6 mm. Effective diffusivity values increased with increasing sample thickness and air temperature and found to be in the range of 1.84 x 10(-7) -3.94 X 10(-7) m(2)/S. The activation energy was 25.4, 25.7 and 29.2 kJ/mol for 6, 9 and 12 mm thickness respectively. (c) 2005 Elsevier Ltd. All rights reserved.