Thin films of novel superhard composite materials consisting of TiN nanocrystals in an amorphous Si3N4 matrix have been prepared by means of plasma chemical vapor deposition. The films show a high Vickers hardness of 5000 kg/mm2 and elastic modulus of ≳500 GPa, and they are resistant against oxidation in air up to ≥800 °C. The theoretical background of these unusual properties are briefly discussed and practical rules suggested according to which similar properties should be expected for composites of other ternary systems.