The technology of drying by hot-air on fruit and vegetable is widely used in practice because of its convenience. However, it has some defects such as a low efficiency and the inferior quality of the dried products, which are the obstacles to its further application. This study focuses on improving the current technology and a new technology is introduced, that is, to dry bio-products by hot-air after they are pretreated by gamma irradiation. Experiments are made to study the influence of different irradiation dosages, air temperatures, slice thicknesses of apple on the dehydration rate and temperature of samples. A conclusion is reached that the three factors affect the dehydration rate and temperature of slice apple, and, the higher the dosage, the greater the rate of dehydration of apple, and the higher the temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.