Until now, only acids introduced in the manufacture of paper and those absorbed from the environment have been believed mainly responsible for the degradation of paper. Experimental evidence is presented to show that significant concentrations of several organic acids are spontaneously generated in the natural aging of all cellulose-based papers, including alkaline papers. Easily detectable concentrations of formic (methanoic), acetic (ethanoic), lactic, glycolic, oxalic and a few other as yet unidentified acids accumulate within a few months of manufacture in paper stored under ambient conditions. It is proposed that the formation of weak organic acids from the oxidation of carbohydrate fragments comprises an essential element of a mechanism for the aging of cellulose. Oxidation and acid hydrolysis reactions reinforce each other in this reaction mechanism to promote an ever-accelerating degradative process. Based upon these findings, a new accelerated aging test for paper has been developed that shows a greater similarity to natural aging than presently accepted accelerated aging methods.