Three fungicides, formaldehyde, thymol and ethylene oxide and the insecticides caequartyl , lindane , and biblio were applied to afnor paper samples. None deteriorated the paper seriously. However, the rag paper proved to be stronger than the chemical pulp paper, and the samples aged before treatment were less altered than those aged after treatment. Ethylene oxide was preferred because it acts as an insecticide as well as a fungicide.