Two fluidized catalytic cracking catalysts were separated using isopycnic density gradient methods. For each catalyst, both the fresh and equilibrium materials were separated. Quite different density distributions were found, not only between the equilibrium catalysts but between the fresh catalyst and its corresponding equilibrium version. In addition, different density distributions were found with different separating media, e.g. aqueous sodium polytungstate or CCl4/tetrabromethane. Crystallinity measurement across the density band for one of the fresh catalysts varied by a factor of 3.