INTRODUCTION AND AIMS: In response to concerns about the prevalence of heroin-related morbidity and mortality, overdose response training programs have been implemented in Victoria, with the aim of improving outcomes after heroin overdose. The aim of this study was to examine reported overdose response by current injecting drug users (IDU) during overdose events, in comparison with previous studies. DESIGN AND METHODS: A total of 99 IDU (median age 35 years, 72% male) were administered a questionnaire that collected information on knowledge and experience regarding recognition of heroin overdose and response. The primary outcome measure was the rate of ambulance notification and expired air resuscitation during witnessed heroin overdose. Data were analysed using descriptive statistics and univariate analysis. RESULTS: Sixty participants had overdosed at least once, and 84% had witnessed an overdose. 78% recognised altered consciousness as a sign of heroin overdose, but less were aware of depressed breathing (42%) or cyanosis (61%). Reported overdose interventions included correct positioning (39%), expired air resuscitation (32%), ambulance notification (76%) and staying with the victim (87%). DISCUSSION AND CONCLUSIONS: Our study has found improved responses to heroin overdose during witnessed heroin overdose among current IDU, compared with earlier work. However, a lack of knowledge regarding appropriate first-aid response persists, which might improve with the development and implementation of training initiatives in this area, ranging from identification of overdose to the administration of life-saving measures.