Titanium aluminum nitride films (Ti1-xAllambdaN) have been deposited by reactive magnetron cosputtering. Elemental compositions of these films have been determined by core level photoelectron spectroscopy. Scanning electron microscopy reveals a columnar film growth. This is also reflected by the topography of film surfaces as studied by atomic force microscopy. By x-ray diffraction a crystalline atomic structure is revealed. Single phase samples can be obtained, consisting of the substitutional solid solution (Ti, Al)N. Crystallites show preferential orientation. The optical properties of these films have been investigated by spectrophotometry in the UV-VIS-NIR wavelength range. Depending on the elemental composition, the optical constants vary from metallic to dielectric behavior. For film compositions with x <0.5 typical features are a tunable transmission maximum and reflection minimum in the visible spectral range, a high infrared reflection, and a low infrared absorption. Due to these optical properties, Ti1-xAllambdaN films are promising candidates for applications such as coatings for solar control windows and optical selective solar absorbers.