Use of the biocide polyhexamethyleneguanidine for treatment of paper in the Soviet Union is described. It is reported compatible with other polymers used in conservation and in combination with polyacrylamide and polyamidamine, results in improved paper permanence and resistance to wear. Its presence does not prevent subsequent optical or photographic study of treated paper. Hygienic and toxicological tests show it to be safe for warm-blooded animals.