A high surface area (∼22 m 2/g) micro-sized (0.3–2 μ) barium hexa-aluminate powder was prepared by the calcination (at 1400 °C for 2 h) of hydrothermally prepared precursors of orthorhombic barium carbonate and boehmite. The precursors were obtained by a hydrothermal treatment (at 180 °C, for 1 h) of aqueous solutions of barium and aluminum nitrates of appropriate compositions in the presence of aqueous urea as the neutralizing precipitant. Results of XRD, TG-DTA and SEM measurements suggest the most probable reaction sequence for the preparation of barium hexa-alumnate ceramic powder as: (i) the hydrothermal precipitation of orthorhombic BaCO 3 and boehmite (γ-AlOOH) precursors from the aqueous Ba and Al nitrates in the presence of urea, (ii) the formation of an interim mixture of γ-Al 2O 3, BaCO 3 and Ba–β 1-alumina in the temperature range of 800–1200 °C, and finally (iii) the formation of a ceramic powder corresponding to the composition BaO·6Al 2O 3 having β-alumina type structure at ∼1400 °C. The final material did not show presence of any other crystalline phases like alumina, baria, barium mono-aluminate and tri-barium mono-aluminate phases.