A new method for the addition of sodium to cracking catalysts in a cyclic deactivation unit (CDU) has been established. Sodium was added to a commercial residue FCC catalyst via an aqueous solution of sodium chloride prior to the cracking step in the CDU. The deactivated samples were characterised and tested in a microactivity test (MAT). The effect of sodium chloride deposition was compared with the effect of sodium naphthenate added via the cracker feed of the CDU. The results show that the addition of sodium chloride up to a level of 5000 ppm sodium give similar changes in catalyst behaviour and characteristics as when sodium naphthenate is used as the sodium source. The addition of up to 5000 ppm sodium leads to a significant decrease in the zeolite content, a certain reduction in activity and hydrogen yield, and a reduction in the extent of hydrogen transfer reactions. The results indicate that sodium chloride leads to a smaller decrease in the hydrogen transfer reactions compared to the addition of sodium naphthenate when 5000 ppm sodium is added. Sodium does not affect the gasoline octane numbers significantly.