Decisions about the treatment of a painting depends on an interdisciplinary investigation. Provides three examples out of the daily practice of cleaning, retouching, and lining. Discusses a cleaning controversy in the restoration of the large <i>Citizen's Guard</i> paintings by Frans Hals. Although the advisory committee concluded that the thick, yellowed, and irregular varnish had to be removed, it appeared that a thin layer of most probably oil varnish remained after cleaning with a fast-evaporating solvent. It was decided that this thin layer was to be left in order to save the painting for a more thorough treatment. The result was a compromise in the degree of cleaning. The second case was the painting of <i>Mercury</i> by Hendrik Goltzius. The red drapery on which Mercury is sitting had been overpainted in an earlier restoration. The original red was very thin and the restorer had not been aware of Goltzius's technique as a graphic artist. He had used the cool grey ground paint in modeling shapes and shades in the drapery, so the paint was not worn but originally locally thin or absent. The third example concerns a 17th-century painting by Jan van Kleef, which had apparently not been lined. This being an exception, it is worthwhile maintaining the painting as much as possible in an untreated condition, leaving the original back and edges visible, showing the traces of the 17th-century method of stretching a linen cloth within a stretcher by means of strings. The dream of the unrestored object is actualized, the first treatment being too high a threshold. A very cautious treatment was chosen for the preservation of the painting.