Owing to a number of their peculiar properties (the presence of the combination of various organic and mineral substances, high hygroscopicity), leather and parchment are damaged by microorganisms easily. Damage of these materials, caused by microbes, often takes place under storage conditions in museums. In spite of this, the problem dealing with microorganisms growing on leather and parchment has not been extensively explored. This paper is a study of microorganisms damaging leather and parchment, an investigation of influence exerted on their growth by the environment, and finding a method of disinfecting the damaged parchment.