Fatal poisonings among young drug addicts (15-34 years) in the five Nordic countries, Denmark, Finland, Iceland, Norway and Sweden in 1991 were investigated and compared to a similar investigation for 1984-1985 (Sweden for 1984 only). A common definition of 'drug addict' has been applied by the participating countries. In both investigations, the greatest number of drug addict deaths was seen in Denmark calculated per 10(5) inhabitants, followed in descending order by Norway, Sweden, Finland and Iceland. An increased number of deaths was observed from 1984-1985 to 1991 in all five countries. The increase in Denmark and Sweden was small while the number of deaths was more than doubled in Norway and Finland. The increased number of cases in Norway and Sweden in 1991 is mainly due to a greater number of deaths in the age group 25-34 years. In Finland, the increased number was seen mainly in the age group 15-24 years. In the two investigations heroin/morphine caused most of the fatal poisonings in Norway and Sweden. In Denmark, heroin/morphine caused about half of the fatal poisonings only, and strong analgesics other than heroin/morphine caused about one third of the deaths. In 1984-1985 it was methadone, propoxyphene and ketobemidone and in 1991 mostly methadone. The number of heroin/morphine related deaths in Finland increased from 1984-1985 to 1991, but other drugs and poisons caused a much higher proportion of the deaths. Pentobarbital caused the only fatal poisoning in Iceland in 1991.