The aim of the investigation was to study the influence of the standing time of the extrudate prior to spheronization and the speed of rotation expressed as linear peripheral velocity of the spheroniser plate on the properties of pellets using a 5(2) factorial experiment. Pellets composed of diclofenac sodium (5%), lactose monohydrate (20%) and microcrystalline cellulose (75%), prepared with water as the liquid binder (total solids to liquid ratio 1:0.675) using a screen extruder were produced after various standing times of the extrudate (ranging from immediate spheronization to 2 h) and at different rotational speeds ranging from 770 to 2900 rpm, which translates into a linear peripheral velocity of the friction plate from 4.84 to 18.22 m/s. The relative yield in the practically used pellet size fraction of 0.71-1.44 mm depended significantly on the standing time of the extrudate. Pellets produced at the lowest linear peripheral velocity were not round, and this was not affected by the standing time of the extrudate. Both the surface tensile strength and the density of the pellets were related to the extrudate standing time and the linear peripheral velocity, whereby the two factors were found to interact. However, neither of the process parameters nor the pellet properties themselves appeared to have an influence on the dissolution of the drug. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.