An electrical contact interface is visualized by rendering 'contact maps' from x-ray computer tomography images without the need for dismantling the specimens. The contact maps consist of approximately 1500 × 1500 pixels with each pixel relating to a 8.0 µm × 8.0 µm area at the interface. The specimens consist of bolting a cable lug to a printed circuit board at various contact normal forces between 0.8 and 3.2 kN. Quantitative analysis of the contact maps gives values for the mechanical area of contact and the size distribution of the contact spots. The size distribution of the spots shows a fractal behaviour analogous to the size distribution of islands on Earth. Data on the spot size distribution of the electrical contact interface are presented. The contact maps also give information on the geometry of contact spots and their spatial distribution over the apparent area of contact.