The method of scaling-up test rig data to full-scale installations, previously used quite extensively in the design of pneumatic conveying systems, is shown to be inadequate in particular applications. Two popular forms of definition and three existing empirical relationships for the solids pressure drop component are modified to demonstrate the possible extent of this inadequacy. Steady-state pipeline conveying characteristics obtained from three products (fly ash/cement mix, PVC powder, screened coke) and four test rigs are used in the development of an improved scale-up procedure. Suggested methods to predict air-only pipeline pressure drop (for both single-and stepped-diameter pipelines) and to generalise pneumatic conveying characteristics for a particular material (applicable to any system of different length and/or diameter) are also included. © 1987.