The prescribing of opioid analgesics for pain management—particularly for management of chronic noncancer pain (CNCP)—has increased more than fourfold in the United States since the mid-1990s. Yet there is mounting evidence that opioids have only limited effectiveness in the management of CNCP, and the increased availability of prescribed opioids has contributed to upsurges in opioid-related addiction cases and overdose deaths. These concerns have led to critical revisiting and modification of prior pain management practices (e.g., guidelines from the Centers for Disease Control and Prevention), but the much-needed changes in clinical practice will be facilitated by a better understanding of the pharmacology and behavioral effects of opioids that underlie both their therapeutic effects (analgesia) and their adverse effects (addiction and overdose). With these goals in mind, this review first presents an overview of the contemporary problems associated with opioid management of CNCP and the related public health issues of opioid diversion, overdose, and addiction. It then discusses the pharmacology underlying the therapeutic and main adverse effects of opioids and its implications for clinical management of CNCP within the framework of recent clinical guidelines for prescribing opioids in the management of CNCP.