Radionucleides can penetrate into the body via the lung, the digestive tract, wounds and sometimes through healthy skin. Once they have penetrated the body, they can either remain localized at the site of entry or be rapidly metabolized. The risk is late effects. Radioelements must be eliminated as rapidly as possible decreasing the exposure proportionally. The effectiveness of the treatment depends on early institution. Nevertheless, emergency intensive care or surgery may be required. As soon as possible, explorations must be carried out to evaluate the level of contamination (human spectrometry, radiotoxicological examinations) and to start treatment. Modalities include non-specific techniques (lavage, insolubilization, laxatives) and specific techniques such as complexation or isotopic dilution (iodine for iodine, Prussian blue for cesium, DTPA for plutonium, Diamox or sodium bicarbonate for uranium). Surgical cleaning of wounds and burns is an excellent means of decontamination. External contamination is often associated. Further contamination must be prevented immediately.