In response to periodontal pathogens, the leukocytes (PMN) elaborate destructive oxidants, proteinases, and other factors. The balance between these factors, the antioxidants and endogenously synthesized antiproteinases determine the extent of periodontal damage. Malnutrition (PEM) is characterized by marked tissue depletion of the key antioxidant nutrients, including GSH (gamma-glutamyl-cysteinyl-glycine), and impaired acute-phase protein response (APR) to infections. The latter results in diminished production of the acute-phase proteins (APP). The APR plays a key role in promoting healing, and its deficit in PEM is due to impairment in the production and cellular action of the cytokines. Other features of malnutrition include inverted helper-suppressor T-cell ratio, histaminemia, hormonal imbalance with increased blood and saliva levels of free cortisol, and defective mucosal integrity. Malnutrition, particularly of the PEM type which usually involves concomitant deficiencies of several essential macro- and micronutrients, therefore has the potential to adversely influence the prognosis of periodontal infections.