A single crystal of fully dehydrated fully Cd2+-exchanged zeolite X, Cd46Si100Al92O384 per unit cell, was exposed at 320 degreesC to 0.005 Torr of Cd vapor for 9 days. The resultant crystal, Cd(68)Si(100)A(192)O(384) per unit cell [a = 24.953(6) Angstrom], was determined by single-crystal X-ray diffraction techniques in the cubic space group Fd (3) over barm at 21(1) degreesC. The structure was refined to the final error indices R-1 = 0.073 and R-2 = 0.100 with 249 reflections for which I > 3sigma(I). In this structure, Cd species (formally Cd2+, Cd+, and Cd-0) are found at seven crystallographic sites. Twenty-eight Cd2+ ions per unit cell are found at three crystallographic sites: eight occupy site I' in the sodalite unit and associate with four Cd-0 atoms near site II' to form four (Cd-3)(4+) clusters [Cd2+-Cd-0-Cd2+ = 105.2(7)degrees, Cd2+-Cd-0 = 2.76(5) Angstrom, Cd2+-O = 2.176(25) Angstrom, Cd-0-O = 3.03(5) Angstrom] in four of the eight sodalite cavities per unit cell. The remaining 20 Cd2+ ions are found at sites II' and 11 with occupancies of six and 14 [trigonal, Cd-O = ca. 2.19(2) Angstrom for both]. Thirty-six Cd+ ions are found at three crystallographic sites: six Cd+ ions are at site 1, at the centers of the double six-oxygen rings [octahedral, Cd-O = 2.559(14) Angstrom]; 18 Cd+ ions lie at site I', in the sodalite cavity opposite double six-oxygen rings [trigonal, Cd-O = 2.393(25) Angstrom]; and 12 Cd+ ions occupy site 11 in the supercage [trigonal, Cd-O = 2.418(23) Angstrom]. Of the 46 Cd 21 cations initially present per unit cell, 18. have reacted to form 36 monatomic Cd+, and eight associate with four Cd-0 atoms to give four (Cd-3)(4+) cations. Highly reducing cadmium species are highly dispersed within the zeolite.