Ce4Al2O9, the last missing member of a family of lanthanide aluminates with 2Ln(2)O(3)-Al2O3 stoichiometry has been synthesized by the reaction between nanocrystalline CeO2 and an amorphous Al2O3 at 850 degrees C in hydrogen atmosphere. The Ce4Al2O9 is isomorphous with known Ln(4)Al(2)O(9) (Ln = La, Nd-Lu) aluminates and its structure is: P2(1)/c, a = 7.844 angstrom, b = 10.968 angstrom, c = 11.399 angstrom, = 109.65. The volume of the unit cell of Ce4Al2O9 synthesized in this work (923.6 angstrom(3)) fits the pattern determined for other lanthanides, if cerium is present as Ce3+ ions. The compound exhibits paramagnetic behavior at 100-400 K, but the effective moment of Ce ions ((eff) = 1.36) is much less than 2.5 waited for Ce3+ ions. The effect is assigned primarily to the surface oxidation of Ce4Al2O9 at ambient conditions, though the presence of certain fraction of tetravalent Ce ions in the structure of Ce4Al2O9 may not be excluded.