Thirty female Sprague-Dawley rats (250 +/- 10 g) were divided randomly into five equal groups. After overnight fasting, a silastic catheter was placed in the jugular vein of each rat. Each group was intragastrically administered 0.25 mg F/250 g rat weight in 1 ml of one of the following forms of fluoride supplements: Pediaflor (Abbott/Ross, Columbus, OH), Tri-Vi-Flor, Tri-Vi-Flor + iron; Poly-Vi-Flor or Poly-Vi-Flor + iron (Mead Johnson Nutritionals, Bristol-Myers Squibb Co., Evansville, IN). Timed blood samples were collected and plasma fluoride concentration was determined using the microdiffusion method. The presence of iron and vitamins affect the bioavailability of fluoride as measured by the area under the time-plasma fluoride concentration curve.