In 2016, 63,632 drug overdose deaths occurred in the United States, 42,249 (66. 4%) of which involved opioids (1). The development of prevention programs are hampered by a lack of timely data on specific substances contributing to and circumstances associated with fatal overdoses. This report describes opioid overdose deaths (referred to as opioid deaths) for decedents testing positive for prescription opioids (e. g. , oxycodone and hydrocodone), illicit opioids (e. g. , heroin, illicitly manufactured fentanyl, and fentanyl analogs), or both prescription and illicit opioids, and describes circumstances surrounding the overdoses, in 11 states participating in CDC's Enhanced State Opioid Overdose Surveillance (ESOOS) program. * During July 2016-June 2017, among 11,884 opioid overdose deaths, 17. 4% of decedents tested positive for prescription opioids only, 58 VSports手机版. 7% for illicit opioids only, and 18. 5% for both prescription and illicit opioids (type of opioid could not be classified in 649 [5. 5%] deaths). Approximately one in 10 decedents had been released from an institutional setting in the month preceding the fatal overdose. Bystanders were reportedly present in approximately 40% of deaths; however, naloxone was rarely administered by a layperson. Enhanced surveillance data from 11 states provided more complete information on the substances involved in and circumstances surrounding opioid overdose deaths. Consistent with other emerging evidence and recommendations,† these data suggest prevention efforts should prioritize naloxone distribution to persons misusing opioids or using high dosage prescription opioids and to their family members and friends. In addition, these data suggest a need to expand treatment and support for persons who have experienced a nonfatal overdose and to expand treatment in detention facilities and upon release. .