In this study, a Szegvari type vertical mechanical alloying/milling attritor was designed and constructed for research purposes. By using this attritor, optimum processing parameters such as milling time, milling speed (rpm), diameter and the amount of the milling balls, milling atmosphere and raw material properties were determined when mechanical milling of gas and water atomised 17-4 PH stainless steel powders. After milling, powder size analyses and microscopic studies were carried out for the characterisation of as-received and milled powders. It was observed from the results of the present investigation that for 17-4 PH stainless steel powders, optimum properties were obtained when milling was carried out at 500 rpm in an inert atmosphere by using 250 g of 10 mm diameter balls. © 2005 Elsevier Ltd. All rights reserved.