The objective of this study was to determine the drying behavior of 2-phase olive mill waste (2POMW) under isothermal microwave-convection drying conditions. 2POMW samples were dried in a thin layer in a variable-power pilot microwave oven with impinging air, using a feedback controller to maintain sample temperature at one of four levels. Moisture loss and shrinkage of the samples were recorded during drying. The apparent diffusion coefficient of water was determined for the first falling rate period both with and without shrinkage. Apparent diffusivity was 28% lower when shrinkage was considered. Thus, shrinkage plays an important role in the drying behavior of this agricultural residue. Published by Elsevier Ltd.