Several gravimetrical properties of five varieties of pistachio and its kernel (Akbari, Badami, Kalle-Ghuchi, Momtaz and O'hadi, which are major commercial Iranian pistachio varieties) were investigated and compared in terms of unit mass, shell ratio, peeling loss, true volume, true density, bulk density, porosity, at five moisture contents levels in the range from initial moisture content at harvesting to completely industrial dried condition. Peeling loss percentage of all varieties was between 38.26% and 43.39%, whereas shell ratio percent obtained between 43.54% and 47.10%. The unit mass of Akbari, Badami, Kalle-Ghuchi, Momtaz and O'hadi pistachio nuts were 1.334-1.696, 1.014-1.250, 1.599-2.234, 1.081-1.403, 1.105-1.680 g, respectively. However, the range of unit mass for Akbari, Badami, Kalle-Ghuchi, Momtaz and O'hadi pistachio kernels were 0.723-0.873, 0.553-0.743, 0.832-1.277, 0.524-0.759, 0.547-0.873 g, respectively. The true volume of Akbari, Badami, Kalle-Ghuchi, Momtaz and O'hadi pistachio nuts obtained between 1.602 and 2.206, 1.175 and 1.422, 1.857 and 2.589, 1.256 and 1.628, 1.291 and 1.873 cm(3). However, the range of true volume for Akbari, Badami, Kalle-Ghuchi, Momtaz and O'hadi pistachio kernels were 0.838-1.116, 0.642-0.854, 0.965-1.474, 0.609 0.874, 0.634-1.013 cm(3), respectively. The effect of moisture content on unit mass, volume, true density, and bulk density of pistachio nuts and their kernels showed a linear increase with increasing moisture content. However, the porosity decreased linearly with the increasing moisture content in pistachio nuts and their kernels. (c) 2006 Elsevier Ltd. All rights reserved.