Tablets produced in the pharmaceutical industry consist of more than one component. The densification behaviour, the compaction properties of a formulation are strongly influenced by the characteristics of the mixture, e.g. the particle size fractions of the components. Direct compression is a well-known and simple method in tablet manufacturing. It has a number of advantages, the greatest of which are the saving of time, labour and cost. It involves only a few processing steps from beginning to end, as compared with up to a dozen steps for wet granulation. However, direct compression also has certain disadvantages: the physical limitations of the drug and the physical properties of the raw materials present become more critical and must be controlled more precisely. We studied the compressibility of some excipients commonly used in pharmaceutical technology, both alone and in binary mixtures. With this aim, we compressed the materials into tablets with a Korsch EKO instrumented eccentric tablet machine (Emil Korsch Maschinenfabrik, Berlin, Germany). The compression tools were flat-faced bevel-edged punches 8 mm in diameter with a halving line on one side, equipped with strain gauges and a displacement transducer. The binary mixtures were compared through the use of compression cycles and energetic parameters. (c) 2008 Elsevier B.V. All rights reserved.