A process and apparatus for fluidized bed catalyst regeneration. The regenerator contains a base fluidized bed, a bubbling dense bed above the base fluidized bed, and a dilute phase region above the bubbling dense bed. The bubbling dense bed has a larger cross sectional area than the base bed. Most, preferably all, the regeneration gas is added to the base fluidized bed. Higher superficial vapor velocities in the base fluidized bed, with conventional vapor velocities in the bubbling dense bed, allow more efficient regeneration in the base bed, without excessive catalyst entrainment into the dilute phase. Regenerated catalyst may be recycled from the bubbling dense bed or the dilute phase to the base fluidized bed, preferably via a cyclone dipleg.