The study is based on autopsies of 86 drug addicts who died during the period 1986-88 after an opiate ingestion. The average postmortal concentration of morphine after ingestion of heroin was 0.88 mumol/l blood, ranging from 0.0 to 3.1 mumol/l, which is substantially lower than values that have been reported from patients receiving morphine intravenously as an analgetic. Postmortal blood concentrations of morphine were significantly lower among deceased with only fresh needle marks than among deceased with both old and fresh needle marks, suggesting that a pause in the drug abuse may have led to a decrease in opiate tolerance. There was no relationship between the detected organ pathology finding of other ingested substances and the postmortal concentration of morphine. In 20% (n = 17) of the deceased the HIV-antibody test was positive and the average blood concentration of morphine was higher in this sub-population than in the rest of the cases.