Boron nitride has for the first time been deposited from gaseous BBr3 and NH3 by means of atomic layer deposition. The deposition temperatures were 400 and 750 degreesC, and the total pressure was 10 torr. The BN films, deposited on silica substrates, showed a turbostratic structure with a c-axis of 0.70 nm at a deposition temperature of 750 degreesC as determined by X-ray diffraction. The films deposited at 400 degreesC were significantly less ordered. The film density was obtained by means of X-ray reflectivity, and it was found to be 1.65-1.70 and 1.90-1.95 g cm(-3) for the films deposited at 400 and 750 degreesC, respectively. Furthermore, the films were, regardless of deposition temperature, fully transparent and very smooth. The surface roughness was 0.3-0.5 nm as measured by optical interferometry.