The primary focus of this review deals with questions of the health risk involved in therapy with calcium-disodium edta (60004) and especially the use of prophylactic chelation therapy, particularly under conditions of continued exposure to lead (7439921). Topics include effects of chelating agents on excretion of lead from the body and on blood lead levels, effects on symptoms of lead poisoning, effects upon the kidneys, increased absorption of lead from the gastrointestinal tract, t-wave changes in electrocardiograms, effects on the metabolism of other trace metals, prophylactic chelation programs, previous reviews of chelation therapy, and recent studies and related actions. A table gives a summary of the beneficial and adverse effects associated with chelation therapy in man. It is concluded that chelating agents are useful in the therapy of acute overexposure to lead. However, prophylactic use of chelating agents, particularly under conditions of continued exposure to lead can be harmful to health. Potential adverse effects include kidney damage, symptomatic lead poisoning, increased absorption of lead from the gastrointestinal tract and disruption in the metabolism of trace metals other than lead. Prophylactic chelation is an unacceptable medical practice which cannot be condoned.