BACKGROUND Large increases in salivary fluoride were reported 1 h after a calcium pre-rinse/NaF rinse. OBJECTIVE This study examined the persistence of these increases. METHODS 12 subjects rinsed in the evening with water, with a 228 microg/g (ppm) F rinse or with 150 mmol/l calcium lactate followed by a 228 microg/g F rinse. In a second experiment these same patients rinsed with a 912 microg/g F rinse. Saliva samples were obtained the morning after rinsing, centrifuged and the supernatants analyzed. RESULTS The Ca pre-rinse/228 microg/g F rinse induced an increase in overnight salivary F over the 912 microg/g F rinse (approximately 2.5 times) and a statistically significant increase over the 228 mug/g F rinse (approximately 5.5 times). CONCLUSIONS The results suggest that a Ca pretreatment may increase the cariostatic effect of topical F agents.