Real time spectroscopic ellipsometry (RTSE) was employed to study the optical, electronic, and transport properties of various classes of nanocrystalline nitride coatings grown by reactive unbalanced magnetron-sputtering. The investigated materials include TaZrN and NbZrN solid solutions, and nc-ZrN/Ag and nc-ZrN/Ni nanocomposites. Film properties were tailored by varying film composition. The following models were used to interpret the ellipsometric data: (a) effective medium theories describing the heterostructures in terms of their constituent materials and (b) a combined Drude-Lorentz model describing the optical response of the conduction and valence electrons. A correlation was found between the optical data and the chemical composition using the linear and Bruggeman effective medium approximations for the solid solution and the nanocomposite materials, respectively. The Drude-Lorentz model provided extensive information regarding the optical and electronic properties of the films (plasma frequency, electron mean free path, electrical resistivity, and band structure). For example, a correlation was made between the conduction electron mean free path and the grain size in nanocomposite films. RTSE findings were confirmed using x-ray diffraction, transmission electron microscopy, and x-ray photoelectron spectroscopy. (C) 2004 American Vacuum Society.