Saliva plays a central role in the formation of oral malodor. Such formation has as its basis bacterial putrefaction, the degradation of proteins, and the resulting amino acids by microorganisms. Saliva provides substrates that are readily oxidized and in the process facilitates oxygen depletion. This favors the reduced conditions conducive to production of odoriferous volatiles. At the same time, saliva is a major source of oxygen for the oral bacteria which generally is inhibitory of their formation. The pH is also critical to malodor development; acidity inhibits, whereas neutrality and alkalinity favor malodor production. Since the pH on oral mucosal surfaces where odor formation occurs is largely determined by the fermentative and putrefactive activities of the adhering bacteria, these acid-base processes are necessarily of major regulatory importance. Because oral malodor and periodontitis both involve excessive oral putrefaction, a better understanding of putrefaction could lead to more substantive methods of oral malodor treatment than exists today, as well as identifying new approaches to amelioration of the bacterial attack on the soft tissues leading to the destruction associated with periodontal disease.