Carbon nitride (CNx) and diamond-like carbon (DLC) coatings were prepared using dc magnetron sputtering at room temperature. The morphology, chemical composition and bonding state of the coatings were characterized by atomic force microscopy (AFM), Auger electron spectroscopy (AES) and Raman spectroscopy. Compared to DLC, CNx, coating exhibited a slight improvement in hardness, coefficient of friction, roughness, and corrosion. The effects of CNx and DLC coatings on cultures of mouse fibroblasts and human endothelial cells were determined by scanning electron microscopy. The results showed that the coatings caused no adverse effects on the cells. CNx coating provided a comparable or better surface for the normal cellular attachment, growth, and morphology as compared to DLC. These results support the biocompatibility of both CNx and DLC and should initiate an interest in the biomedical applications of CNx coating.