Opioids are responsible for 25 percent of constipation in terminally ill patients. Patients in pain require prophylaxis to prevent opioid bowel syndrome (OBS). Laxatives are the treatment of choice, but are marginally effective. The development of quaternary opioid receptor antagonists is a step toward target-specific therapy for opioidinduced bowel dysfunction. This review will discuss the pathophysiology and management of OBS.