With the increased use of various fluoride preparations for caries prevention, all dental personnel should know their potential toxicity and the margins of safety associated with their use. An understanding of the body’s mechanisms for handling fluoride provides a rational basis for assessing the possible risks of excessive fluoride ingestion. Five to 10 grams of sodium fluoride is considered a Certainly Lethal Dose (CLD) for a 70 kg adult. One quarter of the CLD can be ingested without producing serious acute toxicity, and is known as the Safety Tolerated Dose (STD). CLDs and STDs for most commonly used fluoride agents and procedures show that they can be applied with little or no risk of adverse effects, as long as they are handled judiciously. If their use is abused, there is a risk of illness or even death. If amounts of fluoride close to the CLD are ingested, the speed of initiating proper treatment is critical for survival. Vomiting should be induced, if it is not spontaneous; fluoride-binding liquids, such as milk, administered; and the patient taken to the nearest hospital for emergency care. Frequent ingestion of low, but excessive quantities of fluoride during the period of tooth formation can lead to dental fluorosis. Particular concern is warranted for the ingestion of fluoride-containing toothpastes by young children and the inappropriate use of dietary fluoride supplements in communities with sufficient fluoride already present in drinking water. Parents should brush the teeth of preschool children or, at the very least, dispense only small amounts of toothpaste for them (a pea-size portion). Dentists and physicians should know the fluoride concentration of a patient’s water supply before prescribing fluoride supplements. Fluoride preparations should be dispensed in appropriate quantities; labeled with suitable cautionary statements; packaged, when appropriate, with childproof closures or in tearproof materials; and stored in safe locations. Practitioners should use only FDA- or ADA- approved products, employ recommended methods for their delivery; know their toxicity; and be familiar with emergency measures for treating accidental overdosages. The risk of adverse effects is small, when fluorides are handled judiciously.