Questions which must be answered in a museum laboratory are: what is the nature, composition, structure, the state of deterioration and its causes on an art object? Possible methods of examination are x-ray, ultraviolet, infra-red, spectrography, microchemical analysis, and microscopy. The author discusses climate control in museums as well as the maintenance of a proper degree of light and the reasons behind these considerations. The different classes of art objects-organic, metals and alloys, siliceous and equivalent materials, easel and mural paintings-are discussed in terms of their different types, factors and rates of deterioration. The treatment of museum objects must be satisfactory from both a technical and an aesthetic point of view. The author suggests that with paintings, there is a difference between restoration and conservation, that conservators of monuments deal in objective restoration and that archaeological conservators do objective conservation. There are a number of plates for illustration. -- AATA