HY zeolite catalysts on montmorillonite, pillared with aluminum hydroxo complexes in different concentrations, have been tested in the cracking of heavy vacuum gas oil (VGO) from the Shymkent refinery (Kazakhstan). It has been shown that the VGO cracking activity of the catalysts is directly related to the textural and acid properties of the samples. The hydrocarbon group and fractional compositions of cracked gasoline have been determined.