Nutritional and physical properties of ripe hackberry fruits (Celtis australis L.) from Kastamonu were determined. Ash, crude oil, crude energy, crude fiber, crude protein and minerals (Na, P, K, Ca, Mn, B, Ba, Se, etc.) contents of completely ripe fruits were determined. Also, physical properties such as length and diameter of fruit, unit mass, volume of fruit, geometric mean diameter, sphericity, surface area, bulk density, fruit density, porosity, projected area, terminal velocity, 1000 fruits mass, static and dynamic coefficient of friciton were measured at three moisture content levels. The average length, diameter, unit mass, volume of fruit, the geometric mean diameter, sphericity and surface area were established as 9.34 mm, 8.07 mm, 0.233 g, 277.85 mm(3), 8.37 mm, 0.89 and 206.4 mm(2) at 15.25%, respectively, moisture content (w.b.). Studies on rewetted fruit showed that as moisture content increased from 15.25% to 50.42% wet basis (w.b.), bulk density decreased from 595.1 to 535.9 kg/m(3), fruit density increased from 826.1 to 1105.9 kg/m(3). The porosity, projected area, terminal velocity, 1000 fruit mass increased from 30.97% to 53.84%, from 54.91 to 74.63 mm(2), from 4.73 to 10.47 m/s, from 247.5 to 594 g, respectively, for the same moisture increase. The coefficient of static friction on rubber, plywood and galvanized steel increased from 0.5 to 0.55, 0.41 to 0.54 and 0.30 to 0.48, respectively, when the fruit moisture content increased from 15.25 to 50.42%. The coefficient of dynamic friction increased from 0.36 to 0.5, 0.31 to 0.43 and 0.22 to 0.35 on rubber, plywood and galvanized steel, respectively, for the same moisture range. (C) 2002 Elsevier Science Ltd. All rights reserved.