A sample of 329 heroin users were interviewed regarding their personal experience of non-fatal heroin overdose. Experience of overdose was widespread, with two-thirds of subjects (68%) reporting having overdosed. The median number of life-time overdoses was three, with males and females equally likely to have overdosed. The majority (62%) of most recent heroin overdoses occurred in conjunction with the consumption of other central nervous system depressants (alcohol, benzodiazepines and other opioids). Logistic regression analyses indicated three independent factors associated with having overdosed: longer heroin using careers, greater heroin dependence and higher levels of alcohol consumption. Implications for the reduction in the prevalence and frequency of overdose are discussed.