Fluoridated dental care products are used to prevent dental decay. Up to now, there are no data available on whether the fluoride (F-) component of these products affects the bactericidal activity of salivary polymorpho-nuclear leucocytes, which are involved in the protection of the oral mucosa against infection. Therefore, after determining the concentration/time profile of F- in mixed saliva of healthy subjects after topical application of 0.5 g of a 1.25% F- containing gel, unstimulated and fMLP-stimulated polymorphonuclear leucocytes (PMNs) were shortly exposed to these F- concentrations and the generation of superoxide and hypochloric acid were measured, as well as the liberation of lysomal enzymes, and correlated with the cellular Ca2+ and cAMP-levels. The results show that F-, at concentrations as retained in saliva, did not activate the oxidative burst in unstimulated PMNs. In fMLP-activated PMNs, F-suppressed the receptor-mediated increase in the oxidative burst and the liberation of fl-glucuronidase by reduction of the availability of extracellular Ca2+ and, thus, the influx of Ca2+ necessary to couple completely the fMLP signal to effector pathways. These F- concentrations neither altered the liberation of Ca2+ from internal stores nor induced a rise in cAMP. The possible clinical consequences of these results for xerostomic patients with respect to the generation of HOSCN/OSCN/SCN in saliva an important non-immune factor for oral health, are dicussed.