Since 1963 the famous cave of Lascaux has been closed to the public because of the green sickness or algae growth and the white sickness or development of opaque calcite crystals encouraged by the rise in temperature, humidity, and carbon dioxide. A faithful replica, Lascaux II, located 200 meters from the original cave (near Montignac, Dordogne) was completed in 1983. This account describes the methods and materials used to reproduce the ceiling of the cave to actual size on a metal and cast concrete support modelled from contours plotted in situ by stereophotogrammetry, measured to the last millimeter. The final layer of special mortar was modelled by a team of 10 sculptors using a machine which localized in space some 2500 noteworthy points. The painter, Monique Peytral, used drawings, projected slides, and 3-D photographs to reproduce tints and textures and replicate the patina of time. Coloring materials were natural, some unpurified and from the cave itself or from neighboring sites. A small museum forms an antechamber to the replica.