Bi-layer tablets have been developed to achieve controlled delivery of different drugs with pre-defined release profiles. However, the production of such tablets has been facing great difficulties as the layered tablets are prone to fracture. In this paper, the compaction behaviour of binary mixtures and bilayer tablets of two common pharmaceutical excipients, Microcrystalline cellulose and lactose, is investigated. The effects of compositions and compaction pressure on the compaction behaviour of binary matrix mixtures and bilayer tablets are also explored. The delamination phenomena during the manufacturing of bilayer tablets and fracture patterns of tablets subjected to diametrical compression are examined using X-ray computed tomography. The mechanical properties of binary and bilayer tablets of the same composition were also determined and compared. It has been shown that for binary and bilayer tablets with the same composition, the apparent crush strength of these binary and bilayer tablets measured from diametrical compression tests were generally comparable for the powders considered in this study. It was also found that, using the same compaction process, the relative densities of the tablets were generally different when different compositions were used, especially when the maximum compression pressure is relatively low. (C) 2008 Elsevier B.V. All rights reserved.