Thin films of the superconducting compound niobium nitride were deposited at atmospheric pressure on fused silica substrates by reaction of gaseous niobium pentachloride with ammonia and hydrogen gases in a fused silica apparatus. Suitable conditions for the preparation of NbN were found by calculating the free energies of reaction for several possible reactions involving niobium chlorides, ammonia, and hydrogen. Niobium nitride films could be formed at substrate temperature ranging from 900°–1000°C. The deposition rate varied with the reaction conditions from 20 to 1500 Å/sec, and deposits ranged from smooth films of polycrystals in which the individual crystal faces were 20 μ in length. The x-ray diffraction data for the NbN films deposited at 1000°C revealed face-centered cubic structure with cube edge of about 4.358 Å. Niobium nitride films prepared by this method had a wide range of resistivities, temperature coefficients of resistance, and superconducting transition temperatures depending on the deposition conditions. The maximum transition temperature obtained was 15.75 K for the films deposited at 900°C.