A technical study was carried out on a hitherto unknown Eyckian drawing. This drawing is clearly related to the left wing of Jan van Eyck’s Diptych with Crucifixion and Last Judgement, in the Metropolitan Museum, New York. It is argued that the drawing has had a specific function in the genesis of the painting. In both works, the artist similarly demonstrates his ability to attend to detail without losing command of the general arrangement. Both works show, in spite of all the details, the same measure of coherence and organisation. The characteristics of the present metalpoint drawing are discussed in comparison with those of accepted Eyckian paintings. The object was first examined with the stereomicroscope, a high-resolution digital microscope, energy dispersive micro X-ray fluorescence (µ-XRF), X-ray diffraction (XRD), fibre optic reflectance spectroscopy (FORS), infrared reflectography (IRR), and digital imaging. Based on careful observations a small number of microsamples were taken to investigate the composition of the support and ground layer. The samples were analysed with various microscopic, spectrometric and chromatographic methods to further characterise inorganic components, fibres and organic substances. Most of the drawing was made with, at least, two different styluses. One type of lines was made with a silverpoint; other lines were made in goldpoint. In both cases the metalpoint lines were not made with the pure metals but with alloys, and efforts were made to quantify the alloy compositions. The results of these analyses are evaluated in relation to contemporary technical sources. Thus we hope to provide material for a proper assessment of the relation between painting and drawing, to address questions of attribution, and to shed more light on the process of transmission of motifs and ideas in Jan van Eyck’s environment.