The pathologist participating in the investigation of a known or alleged poisoning fatality has a multifaceted responsibility. He must search for and recognize anatomic changes produced by the toxic substance, while recalling that many poisons produce no organic injury even when they are present in lethal concentration. He should always preserve sufficient quantities of body fluids, excreta, and viscera in properly labelled containers so that the chemical analyst has adequate material for all possibilities. Frequent consultation with the toxicologist is essential in the interest of expediting the search for the lethal chemical. Ultimately it falls upon the pathologist to establish the cause of death in the light of all the anatomic and chemical findings.