CrNx (0 less than or equal to x less than or equal to 1) thin films were deposited on silicon (100) by DC reactive magnetron sputtering using a wide range of N-2 partial pressures. Composition and crystal structure were determined by X-ray photoelectron spectroscopy and X-ray diffraction, respectively. Nanoindentation hardness and reduced modulus were measured using a Hysitron nanomechanical properties system. Annealing effects on structure and mechanical properties were studied. The presence of Cr. Cr2N and CrN (and mixtures of these phases) has been confirmed and related to the average film composition. With a small amount of N-2 added (pN(2) similar to 0.5%) the strong Cr (110) peak disappears and the hardness of Cr increases significantly. Pure Cr2N was obtained for pN(2) in the range of 7.5-9.5%, while pure CrN was obtained for pN(2) > 20% of the total pressure. The highest hardness was obtained for pN(2) in the range of 10-15% of the total pressure. During annealing (400 degreesC, 2 h), a Cr2N (111) texture appeared for pN(2) in the range of 0.5-10.0% of the total pressure. The hardness and modulus of Cr, Cr2N and CrN increased after annealing.