Ingested lead shotgun pellets and rifle bullet fragments have been shown to be an important source of lead poisoning in water birds, raptors, avian scavengers, and even seed-eating birds. Ingestion of spent lead shotgun pellets by waterfowl and secondary ingestion by Bald Eagles (Haliaeetus leucocephalus) scavenging on waterfowl led to the change of hunting regulations that prohibit the use of toxic lead pellets for waterfowl hunting in the United States. However, bullets containing toxic lead are still widely used to hunt large game animals and "varmints" and are a source of lead in the environment available to wildlife. Basic bullet materials available to the bullet manufacturer include lead alloys, lead with external copper wash, lead core with copper jacket, pure copper, and bismuth. Lead and bismuth are highly frangible, whereas pure copper bullets tend to remain intact after impact. Bullet fragmentation increases the degree of lead contamination in tissue ingested by scavengers feeding on hunter-killed animal remains. Modern bullet design, velocity, composition, and bone impact are significant factors in the character and distribution of lead particles in carcasses, gut piles, and wound tissue left in the field by hunters. Prior to the 1900s, bullets were made entirely of lead. Their velocities were relatively slow (<2000 feet per second), and their tendency to fragment was accordingly lower than that of modern ammunition. Development of smokeless powder in the 1890s increased bullet speeds above 2000 feet (610 m) per second, causing lead bullets to melt in the barrels and produce fouling which reduced accuracy. Copper jacketed lead-core bullets were therefore developed, which permitted velocities that may exceed 3000 or even 4000 ft/sec in modern firearms. Standard hunting bullets now typically travel at 2600 to 3100 ft/sec, speeds highly conducive to fragmentation. Plastic-tipped "hollow-point bullets" used for varmint hunting are actually designed to completely fragment, leaving the entire mass of the bullet to contaminate the carcass. Hunters value bullets that are accurate and have adequate impact and destructive power to humanely kill the target animal. To decrease the incidence of lead exposure in wildlife and in humans that consume game animals, alternatives to traditional lead-based bullets have been and are being developed. These bullets must be proven to be both as accurate and as lethal as traditional lead bullets in producing humane kills before they are accepted for general use by the hunting community. Additionally, they must be reasonably priced. Keywords: Ammunition, ballistics, bullet fragmentation, lead poisoning, hunting, wildlife.