III-Nitrides (GaN, AlN and other compounds) have attracted vast interest due to their unique properties and potential applications in optoelectronic devices operating in the blue and UV spectral regions and for the construction of electronic devices capable of operating under high power and high temperature conditions. Nanocrystalline AlN powder were obtained by AMMONO method, in which nitridization of Al metal occurs in highly chemical active supercritical ammonia using both NH 4 Cl as mineralizer. The experiments were performed in the temperature range of 350-550 o C and pressure of 80-120 MPa in stainless steel autoclaves for up to 5 days. Nanocrystalline AlN were spontaneously nucleated on the lower walls of the autoclaves. The obtained AlN powder was characterized by X-ray diffraction. Nanocrystalline AlN powders with average crystallite size 20-30 nm were produced in the temperature range of 450-550 o C.