Microfocus Computer Tomography (mu CT) is a non-destructive imaging technique that allows visualisation of internal features within non-transparent objects such as sedimentary rocks. With resolution as good as 10 mu m in three dimensions, this technique is highly superior to medical CT widely used in geology and material sciences. Superior resolution is achieved by decreasing the X-ray spot size, which allows a decrease in the penumbra effect and an increase in primary magnification by placing the sample close to the X-ray source. Since polychromatic X-ray sources are used, the technique is not free of artefacts. Application of filtering techniques is recommended to circumvent these artefacts and to achieve good quality images for quantitative analysis. Application of a dual energy approach allows quantification of density as well as effective atomic number distribution of internal features. As the technique acquires data in 3D, mu CT provides an ideal tool to link 2D thin-section petrography to 3D petrophysical measurements or to be used within an upscaling approach. A number of applications and the use of dual energy density and effective atomic number characterisations are presented. Attention is also paid to some of the limitations of this technique. (C) 2000 Elsevier Science B.V. All rights reserved.