For the purposes of this report, a drug-induced death refers to any death in which the underlying cause was due to "an acute episode of poisoning or toxicity to drugs" or "an acute condition caused by drug use where the deceased person was identified as drug dependent." The term "drug" refers to substances classified as drugs, medicaments, or biological substances under ICD-10 guidelines. These drugs may be used for medicinal or therapeutic purposes, or to produce a psychoactive effect. Alcohol, tobacco, and volatile solvents are excluded from the data. In 2001 in Australia there were 1,038 drug-induced deaths registered, constituting 0.8 percent of all deaths in that year. This was a decline of more than one-third from 1999. This decrease in drug-induced deaths was primarily due to a decrease in deaths due to heroin use, largely as a result of a shortage of heroin supply in Australia. Drug-induced deaths were usually the result of an unintentional overdose or the effects of prolonged misuse of drugs. In contrast to accidental drug-induced deaths, suicides that involved drugs did not have any significant change between 1999 and 2001. In 2001 the rates of accidental drug-induced deaths were highest among young adults, peaking at 8 deaths per 100,000 persons among both 25-29 and 30-34 age groups. Because of the pharmacological interactions between different drugs, using a mixture of drugs was more likely to result in adverse health effects, including death, than use of a single type of drug. In 2001, opium, heroin, and other opioids were involved in 36 percent of accidental drug-induced deaths; benzodiazepines were involved in 23 percent of the accidental deaths, and other narcotics and hallucinogens were involved in 18 percent of the accidental drug-induced deaths. The drugs most commonly used in suicides were benzodiazepines, antidepressants, and opium, heroin, and other opioids. 7 tables