A catalyst regeneration process and apparatus for the oxidation of coke from a spent catalyst, said coke being converted to CO, and for the conversion of the CO to CO.sub.2. Hot regenerated catalyst is recycled from a dense bed in the regeneration zone to mix with incoming spent catalyst in a riser-mixer. The riser-mixer operates in dense phase and is supplied with a relatively small amount of a fluidizing medium, preferably air. After the mixing of spent and fresh catalyst is substantially completed, a relatively large amount of a regenerating gas, preferably air, is admixed with the catalyst mixture, and some coke oxidation occurs. The balance of coke oxidation takes place in a downstream-situated regeneration zone of substantially conventional design. The regenerating gas addition is preferably made at the base of a cone-shaped combustor in order to provide a venturi effect which ensures good air-catalyst mixing.