By studying the number and method of homicidal poisoning in Miami-Dade County, Florida; New York City, NY; Oakland County, Michigan; and Sweden, we have confirmed that this is an infrequently established crime.Several difficulties come with the detection of homicidal poisonings. Presenting symptoms and signs are often misdiagnosed as natural disease, especially if the crime is committed in a hospital environment, suggesting that an unknown number of homicides go undetected.In the reported cases analyzed, the lethal agent of choice has changed over the years. In earlier years, traditional poisons such as arsenic, cyanide, and parathion were frequently used. Such poisonings are nowadays rare, and instead, narcotics are more commonly detected in victims of this crime.