2,2',5,5'-Tetramethyl-1, l'-diarsaferrocene, Cl2Hl6-As2Fe, M r = 365, crystallizes in space group P2l/c with Z = 4, a = 6.37(1), b = 11.266(6), c = 17.515 (9) /k, fl = 97.38 (8) ° , d x = 1.95 Mg m -3, g(Mo Ka) = 6.76 mm -~, and F(000) = 720. The datawere collected on an automatic single-crystal diffractometer. The structure was deduced from Patterson and Fourier syntheses based on preponderant heavy-atom contributions. The least-squares refinement yielded R = 0.042. The Fe atom is sandwiched between two n-bonded arsolyl rings which are neither strictly planar, nor strictly parallel, in an eclipsed configuration. The two As atoms lie out of the planar four-membered C moieties by 0.086 and 0.059 /k. The dihedral angle between the two planar C moieties is 6.2 o.