Dosage forms and methods for the controlled release of oxycodone over a prolonged period of time are described. The sustained release dosage forms provide therapeutically effective average steady-state plasma oxycodone concentrations when administered once per day. This once-a-day dosing regimen results in only one peak plasma oxycodone concentration occurrence in each 24 hour period that occurs at a later time after administration and exhibits a lesser magnitude than the peak plasma oxycodone concentration that occurs following administration of oxycodone in an immediate-release dosage form and other prior art extended release dosage forms.