Desorption isotherms were determined at 25 degrees C for Aledo grapes and at between 25 degrees C and 50 degrees C for Muscatel grapes. The efficacy of two physico-chemical pretreatments designed to accelerate grape-drying kinetics was also studied for Muscatel grapes. The isotherms obtained were fitted with various models, among which the GAB equation gave the best fits, and was subsequently used to calculate the monolayer moisture content for each grape variety. Pretreating Muscatel grapes did not greatly alter the optimal conditions for their storage and handling, suggesting that treated and untreated grapes can safely be stored under the same conditions.