Optical coherence tomography (OCT) is a noncontact and noninvasive technique of depth-resolved structural imaging within media that moderately scatter and/or absorb near-infrared light. It originates from diagnostic medicine and has been under consideration for examining art objects since 2003. The results obtained by means of this method are presented in a convenient manner of cross-sectional images (called B-scans in analogy to ultrasonography) that are easy to compare with conventional microscopic stratigraphy analysis. The advantage of OCT lies not only in its noninvasiveness but also in its ability to examine a relatively wide area. The described instrument provides B-scans of 15 mm width and 2 mm depth. Additional scanning in the perpendicular direction gives 3-D information about the spatial structure of the sample. Because of the high speed of data acquisition, the tomograph is capable of 3-D (volume) data collection within seconds. The obvious disadvantage of the method is that the imaging is limited to media at least partially transparent to infrared light. Therefore, OCT is mostly used for examination of transparent and semitransparent structures, such as varnishes and glazes on easel paintings. It is, however, possible to resolve the thickness and structure of these layers noninvasively in as many places as desired. If the axial resolution permits, the superimposed layers of different varnishes, retouches, and primary layers can be differentiated. The method may also be used for identification of the location of certain pigmented layers within the varnish-glaze structure. In this contribution, the applicability of OCT to monitor the removal of secondary strata is shown, using an eighteenth-century painting as an example.