Samples of three plastics (polymethyl methalcrylate; polyvinyl chloride; polyethylene) and natural rubber were immersed in measured quantities of ten different solvents (chosen on the basis of their frequent use by art conservators) and 2 detergent systems. The weight and the dimensions of the samples were recorded before solvent contact, and at specific time intervals after it had begun. The study is still in progress but it indicates that none of the solvents tested can be used safely with plastic. It is suggested that aqueous systems be chosen for use, and if detergent must be used, Triton X-100 should be avoided. Tables, references, list of US suppliers.