A GLC assay was developed for the determination of oxycodone levels in human plasma using a nitrogen-specific detector. The assay was developed for use in bioavailability studies of therapeutic doses of oxycodone. After ingestion of a commerical tablet containing 4.5 mg of oxycodone hydrochloride and 0.38 mg of oxycodone terephthalate by six volunteers, the mean peak oxycodone concentration in plasma was 18.4 ng/ml at 1 hr.