The purpose of this study is to compare the subjective and objective effects of Oxymorphone ER (Opana ER) versus Oxycodone CR (Oxycontin).

Inclusion Criteria:

• Recreational opioid use.
• At least 3 lifetime occasions of recreational use of an oral intact modified-release opioid product.
• BMI within range of 19.0 to 29.9 kg/m2, inclusive, minimum weight of 50.0 kg at screening and Day 0 of treatment period 1

Exclusion Criteria:

• Self-reported history of drug or alcohol dependence in the past 2 years or presence of drug or alcohol dependence in the past 12 months as defined by the DSM-IV, including subjects who have ever been in a drug rehabilitation program.
• Unwillingness or inability to abstain from recreational drug use as required for the study.
• History of acute asthma or other obstructive airway disease or any condition that may increase the risk for respiratory depression, judged as clinically significant by the investigator or designee.
• History of neurologic conditions such as convulsive disorders or severe head injury, judged as clinically significant by the investigator or qualified designee.
• History of Addison's disease, hypothyroidism, pancreatitis, prostatic hypertrophy, or urethral stricture.
• Use of non-prescription or prescription medications or natural health products within 7 days prior to first drug administration in the qualification phase and throughout the study, unless in the opinion of the investigator or designee, the product will not interfere with the study procedures or data integrity or compromise the safety of the subject.
• Uses of Monoamine oxidize inhibitors (MAOIs) within 14 days of first drug administration in the qualification phase and throughout the study.
• Current consumption of greater than 20 cigarettes (or 2 cigars) per day or inability to abstain from smoking (or use of any nicotine-containing sub stance) for at least 14 hours.

AEs were documented in the eCRF and/or source documents, whether considered treatment-related or not related, throughout the study (ie, from first dose of study drug in the qualification phase to 30 days following the last dose of study drug).

AEs were any new (or increased severity of) signs, symptoms, injury, or illness. Conditions existing prior to screening were recorded as the subject's medical history; events occurring from screening until first dose of study drug in the qualification phase were recorded as baseline signs and symptoms. AEs were reported for the safety population.