The hydrocracking properties of Ni, Mo and NiMo sulphides supported on an ultrastable HY zeolite were examined by studying the hydroconversion of n-decane at moderate pressure (3 MPa). All catalysts were found to deactivate during the first hours on-stream, then reaching almost constant conversion values. Their cracking conversions are significantly higher than that of the HY support. A strong imbalance between the hydrogenation and the acidic function of catalysts was observed. The product selectivities did not depend on the conversion and the secondary cracking occurred. In the binary NiMo samples no synergetic effect between the individual Ni and Mo phases was observed. A reasonable correlation between the n-decane steady-state conversions at 598 K, the sulphidation degree of the metals and Bronsted acidities of catalysts were found.