The formation of the bacterial inhibitor, hypothiocyanite (OSCN––) ion, by human salivary sediment was studied in relation to oral health. Persons with good oral health produced significantly more OSCN–– ions than those with poor oral status. However, no relation in the amount of SCN–– ions and the activity of free or cell-bound peroxidase to oral health was found. This suggests that the difference in OSCN–– formation results from differences in endogenous H2O2 production. It is not sure that increased OSCN–– production leads to better oral health, possibly vice versa, but anyway there is a clear positive correlation. About 80% of oral total peroxidase activity was found to be bound