The osmotic-controlled release oral delivery system (OROS®) is an innovative drug delivery technology that uses osmotic pressure as the driving force to deliver pharmacotherapies in many therapeutic areas. In chronic pain management requiring long-term therapy, pharmaceutical technologies that ensure the controlled release of analgesic medications are imperative. In addition, once-daily formulations ensure better patient compliance to prescribed therapies. Hydromorphone was the first opioid to be formulated as a once-daily preparation using OROS® technology. The purpose of this review is to discuss the application of OROS® technology in the field of chronic pain management and to examine clinical trial results for OROS® Hydromorphone. OROS® hydromorphone ensures the constant delivery of hydromorphone over a 24-hour period, and its pharmacokinetic profile is only minimally affected by food and alcohol. Dose-conversion studies have shown that patients with chronic pain can be easily switched from previous opioid therapies to OROS® hydromorphone without a loss of pain control. These studies support the clinical utility of the 5:1 ratio used for the conversion of oral morphine to oral OROS® hydromorphone. Furthermore, once-daily OROS® hydromorphone has been shown to be effective in patients with chronic cancer and non-cancer pain, and it provides similar pain relief to SR morphine and ER oxycodone. In chronic pain management, OROS® products can result in more stable drug concentrations, reduced dosing frequency and an improved safety profile.