Damage of paper by ink may be caused by both chemical and microbial factors. Degradative agents produced by microbial action are organic acids, cellulase, and hydrogen peroxide. The fungi growing most frequently on ink were isolated and investigated for the production of degradative materials. The damaging effect of the possible biological factors on paper was determined as a decrease in the folding endurance and compared with the effect of chemical factors such as acidity and Fe²⁺. Fungal growth in ink was rather poor. Cellulase and organic acids have to be taken into account as agents of biodeterioration but to a lesser extent than the radical mechanisms catalyzed by Fe²⁺.