This article discusses death by carbon monoxide poisoning & the role of the police officer in the investigation of such deaths. The biochemical aspects of CO poisoning are outlined & 6 case histories are presented. It is stressed that the coroner can only determine from his examination, that the death was caused by CO poisoning: the circumstances reported by the investigation officer are necessary to determine whether the death was accidental or the result of homicide or a suicide attempt. (NBB)