PAL-003 is designed to evaluate long-term treatment of subjects who are continuing to take rAvPAL-PEG. Subjects'previous rAvPAL-PEG dosing will continue in PAL-003. In PAL- 003, each subject's dose will be adjusted as needed to attain or maintain blood Phe concentrations of 60-600 µmol/L. rAvPAL-PEG dose will be based on either a subject's weight or will be a fixed dose (subjects who have maintained blood Phe levels to 60-600 µmol/L for at least 2 consecutive weeks and who have maintained a stable rAvPAL-PEG dose for at least 2 consecutive weeks). Doses will be evaluated on an individual basis.