Carbides and nitrides of transition metals such as Ti attract significant interest since they find a wide field of applications ranging from high-temperature structural materials to contact layers in solar cells. In the present study we report on the influence of the bias voltage on the development of TiC x , TiN y , and TiC x N y films (600–3000 Å thick) developed by magnetron sputtering. The TiC x films were deposited by r.f. magnetron sputtering from TiC targets, while the TiN y and TiC x N y films were deposited by d.c. and r.f. reactive sputtering from Ti and TiC targets, respectively. The bias voltage was varied from 0 to 200 V for all three types of film. In-situ spectroscopic ellipsometry (SE) was used in the energy region 1.5–5.5 eV to monitor film characteristics. Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and microhardness measurements were taken to characterize the composition, stoichiometry, structure, quality and integrity of the films as a function of the bias voltage. For the present deposition conditions, the substrate bias voltage was found to have a significant effect on the stoichiometry and structure of all three types of films. The results show that for TiN y , films the substrate bias can promote stoichiometry and structure refinement through resputtering effects. For TiC x and TiC x N y films, substrate bias can influence stoichiometry and structure by increasing reaction probabilities (of carbon and nitrogen, respectively) in the plasma through ionization and plasma activation effects. Mechanistic aspects of the film development process are discussed in view of the in-situ SE results and the post deposition AES, XPS, XRD and microhardness evaluation.