A cleaning plan describes who is cleaning what, when, how and why. Cleaning has in general an esthetical function, along with hygiene and preservation of the premises. In a museum it should be absolutely clear which rooms, parts and surfaces are or are not to be cleaned by the cleaners and which cleansers they are to use. The equipment to be used has to be determined, for the sake of safety of the museum objects, the building and the visitors. The question whether expensive equipment is to be used can be answered by the calculation of the break even point. It turns out that such a point is reached sooner than one tends to think. The arguments for commissioning the cleaning to a professional company are given, but there may be good reasons for working with own cleaning personnel. It is advised to measure the quality of the cleaning by asking the opinion of users and visitors of the museum and by comparing the degree of cleanliness with that in other, similar buildings.