The study was conducted in a triple cross-over on 12 healthy Caucasian volunteers (4 males and 8 females) of an age between 23 and 44 years. The following products were given in a single oral dose in fasting state. 1. Solution of 29.18 mg of sodium fluoride in 80 ml of water (reference NaF solution). 2. Solution of 100 mg sodium monofluorophosphate (CAS 10163-15-2) in 80 ml of water (Na2FPO3 solution). 3. Tablets with 100 mg sodium monofluorophosphate and 1250 mg calcium carbonate (Na2FPO3 + Ca tablets). The three products were equivalent in fluorine content (13.2 mg). The bioavailability of fluorine was evaluated on the basis of the plasma levels and of the urinary excretion of fluoride. After administration of the products, fluoride appeared in blood with a lag time smaller than 0.05 h and invaded the blood with a t1/2 from 0.07 to 0.12 h. The Cmax of fluoride in plasma was 412-466 ng/ml at a tmax of 0.5-0.7 h. The AUCs of fluoride after Na2FPO3 solution and after Na2FPO3 tablets were within the 0.80-1.20 bioequivalence limits with regard to the AUC after NaF solution. The three products can therefore be considered bioequivalent according to the Westlake criteria. In the 24 h following the administration, the urinary excretion of fluoride accounted for 51 +/- 10%, 46 +/- 6% and 47 +/- 8% of the administered dose, respectively for NaF solution, Na2FPO3 solution and Na2FPO3 + Ca tablets. The difference between the three products was statistically not significant and confirms their bioequivalence.(ABSTRACT TRUNCATED AT 250 WORDS)