A factorial experiment was conducted with weanling rats fed a purified diet to determine the influence of dietary lead (0 or 100 ppm) as either lead acetate or lead carbonate on fluoride bioavailability (2 or 10 ppm as sodium fluoride). During the 6-wk study, both forms of lead depressed weight gain, regardless of the fluoride level, despite the fact that food intake was similar for all treatment groups. Both forms of lead produced a small, but significant, reduction in femur and second molar fluoride. This effect, however, could only be demonstrated in rats fed diets containing 10 ppm fluoride, indicating a significant interaction between lead and fluoride for these indices of fluoride bioavailability. This interactive effect between fluoride and lead was also demonstrated for apparent fluoride absorption. Both forms of dietary lead significantly increased the lead concentration of plasma, femur, liver, and kidney, and both forms of lead significantly increased the urinary excretion of delta-aminolevulinic acid. The level of dietary fluoride failed to influence these measurements. We therefore conclude that, although small amounts of dietary lead reduce fluoride bioavailability, small amounts of dietary fluoride do not appear to significantly influence the utilization of dietary lead.