Results from previous studies have shown that pre- and perinatal exposure to lead enhances susceptibility of rats to development of dental caries. A possible explanation for this phenomenon may be that lead complexes with fluoride and renders F insoluble and unable to exert its cariostatic effects.Thus, to explore this hypothesis, 48 desalivated Sprague-Dawley rats were placed in a König-Höfer programmed feeder and received 17 meals of powdered sucrose daily, and water ad libitum as follows: group (1) plain sucrose and sterile distilled water (SDW); (2) sucrose containing 15 ppm F and SDW; (3) sucrose containing 15 ppm F and 10 ppm Pb water; (4) sucrose containing 15 ppm F and 25 ppm Pb water.The highest smooth-surface, sulcal surface caries and severity scores were observed in group I. Animals that were exposed to fluoride showed reduced smooth-surface caries and severity scores. S. sobrinus counts did not differ among the groups.Lead did not interfere with the protective effect of fluoride in the conditions of the present study.