A kinetic study of gasoil cracking has been carried out on USY and SAPO-37 catalysts. In the MAT experiment USY gives a lower cumulative average conversion, its intrinsic activity is higher, but it decays much faster than SAPO-37. This behavior is discussed on the basis of acidity distribution in the catalysts. Because of the differences in hydrogen transfer activity, the order of cracking for USY and SAPO-37 is different, too. Simulation results indicate that, in a commercial FCC unit, a higher conversion should be expected for USY, as long as the contact time is less than or equal to 3.