[en] Rb₂PuCl₆ and K₂PuCl₆ were prepared by heating mixtures of anhydrous PuCl₃ and the respective alkali metal chlorides under high Cl₂ pressures. Their crystal structures were determined by powder X-ray crystallography. Rb₂PuCl₆: hexagonal, space group P6₃mc, a = 7.377 +- 0.002, c = 11.880 +- 0.007 A, Z = 2, V = 279.9 +- 0.3 A³ (per formula), D/sub x/ = 3.69 gcm³. K₂PuCl₆: monoclinic, space group P2m, a = 7.218 +- 0.005, b = 7.611 +- 0.006, c = 10.208 +- 0.007 A, β = 91.59 +- 0.04⁰, Z = 2, V = 280.3 +- 0.3 A³ (per formula), D/sub x/ = 3.14 gcm³. The variable atom parameters were obtained by means of electrostatic calculation to have the maximum Madelung constant. Raman spectra showed two lines corresponding to v₁(A/sub 1g/) and v₅(F/sub 2g) for both compounds. The difference of stability in M₂PuCl₆ (M = K, Rb, Cs) is discussed