There are significant differences in the frequency of CO intoxication and its relation to other not natural causes of death between the autopsy cases of Leipzig (DDR) and Hannover (BRD). While the percentage of all autopsies in Leipzig runs up to 7.6%, in Hannover it runs up to only 1.5%. Beside the well-known cases of not recognized CO intoxication at the autopsy with or without following intoxication of other persons, two concrete cases of not recognized CO intoxication with the survival of the victims discussed. The not noticed CO intoxication followed by the death of the victim is usually considered in medicolegal opinious as "medical malpractice". In cases of survived not noticed CO intoxications this opinion ist only supposed in special cases with longer anamnesis and a typical seasonal rythmic of symptoms.