The graphic documentation of the state of conservation of ancient monuments, and of the conservation processes applied to them, is considered today an essential feature of a serious conservation project. However, such documentation normally produces a vast amount of large-size drawings on paper which is costly to originate and to update; furthermore, it poses serious problems as to handling, storage and consultation. These problems may be solved by the use of computer graphics which allow a rapid update and reproduction of all drawings, once the basic survey data are memorized; furthermore the storage for archival purposes is much easier, considering the small volume that the data occupy in this form. The present paper illustrates some examples, and in particular the "Arch of Septimius Severus", in Rome. In the latter case the computer drawings on which various sets of data were recorded were printed on transparent sheets; this allows to examine drawings one by one or to superimpose a small number of them, in order to explore possible relationships between two or more sets of data.