Eighty-seven cases of medically unattended deaths were autopsied and investigated for alcohol and barbiturate after the general practitioner had certified the death. A detailed survey was made by comparing the mode and cause of death before and after autopsy. After autopsy and chemical analysis, two suicides, one accidental death and two unknown modes of death were found (5%). The high proportion of unknown mode of death was due to the fact that police investigations were not made. The cause of death differed in 30%. It was mostly due to overestimation of ischaemic heart disease, especially acute myocardial infarction, cerebral haemorrhage and because the unknown cause of death could be placed in a definite group after autopsy. Estimated acute myocardial infarciton could only be confirmed in 50% of the cases. Neoplastic disorders as the cause of death was seldom found to be erroneous, but malignancy was undiagnosed in 4% of all cases. It is concluded that doctors should not use acute myocardial infarction as a cause of death unless there is reasonable clinical evidence for the diagnosis, that obscure cases of death should be left to medicolegal investigation, and that the reliability of mortality statistics still has to be improved. The autopsy is still valuable to ensure this extra security.