Many materials commonly used in dentistry today are considered toxic and harmful to health. Among those materials are the base metals mercury, nickel, lead, chromium, cobalt, beryllium, zinc, tin, copper, and many others. We also apply sterilizing agents such as phenol, formocresol and chlorine directly into root canals. All of the phenols and most of the halogens are considered toxic to some degree. This profession has a long history with regard to the use of mercury. Although the focus of this presentation is on the heavy metal mercury, the concepts applied can be readily transferred to most of the other dental materials. A recent Louis Harris poll reported that a clean environment is second only to a happy home life among the desires of adults. It is the dentist's responsibility to protect themselves and their staff as well as the patients from exposure to toxic materials. Most of the technology used by scientists today to uncover hidden environmental hazards was not available even ten years ago. Numerous new illnesses have cropped up from unknown causes, among which environmental exposure to toxics seems to be a most likely suspect. As these investigations continue you can expect to find that many of the most common dental materials will no longer be considered appropriate for use due to their potentially toxic nature. Modern technology has focused on developing techniques for evaluating biocompatibility that look for minimal damage rather than gross disease. But in the telling words of astronomer Carl Sagan, "Absence of evidence is not evidence of absence." In this paper I will review the state of the research on the patient's exposure to mercury from dental fillings, the occupational hazards of dentistry, the environmental impact, and how best to protect the dentist, the patients, and the dental staff from injury. This subject has been a source of controversy for over a century. The reason the argument has lasted so long is because investigators did not rely upon the documented scientific literature. Through the use of modern science we can dispel many of the common myths about dental amalgam.