Nanocomposite Ni/Al2O3films have been produced by electrochemical deposition where 50 and 300 nm Al2O3particles are dispersed in a nickel matrix. These films exhibit considerable enhancements in their hardness in comparison to pure nickel. The strengthening mechanism is explained in terms of an Orowan bowing hardening mechanism and, hence, related to the volume fraction of the reinforcing phase. These films may have application as strong coatings that retain many of the physical properties (e.g., optical, thermal, electrical) of the metal. ©1995 American Institute of Physics.