Atoms of Kr were encapsulated in the cavities of fully dehydrated Cs3Na8H-A by treatment with 635 atm of Kr at 400 degrees C for 5 days, followed by cooling at pressure. The crystal structures of the zeolite before (under vacuum) and after treatment (at 1 arm) were determined by single-crystal X-ray crystallography in the cubic space group Pm3m at 21 degrees C, In the crystal structures of dehydrated Cs3Na8H-A (a 12,256(1) Angstrom, R(1) = 0.054, R(2) = 0.051) and Cs3Na8H-A(5Kr) (a = 12.260(3) Angstrom, R(1) = 0.050, R(2) = 0.047), nearly three Cs+ ions per unit cell were found at the centers of 8-oxygen rings, each 3.39 Angstrom from four framework oxygens and 3.57 Angstrom from four others. Eight Na+ ions per unit cell are located near the centers of 6-oxygen rings, each 2.29 Angstrom from three framework oxygens. Encapsulated Kr atoms are found at three crystallographically distinct positions in Cs3Na8H-A(5Kr). Each unit cell contains one Kr atom at a threefold-axis site in the sodalite unit (Kr(1)), two opposite 4-oxygen rings in the large cavity (Kr(2)), and two on threefold axes in the large cavity (Kr(3)). They interact weakly with the zeolite (and with each other) by polarization in its electrostatic field. The atom at Kr(1) is near the center of a sodalite unit, consistent with a theoretical calculation of London dispersion energy in sodalite. Kr(1) is 3.39(4) Angstrom from a Na+ ion and 3.87(2) Angstrom from the three framework oxygens; Kr(3) has a similar environment with distances of 3.23(2) and 4.16(2) Angstrom. Each atom at Kr(2) is 3.81(3) Angstrom from four 4-ring oxygens. The four Kr atoms in the large cavity form a rhombus [-Kr(2)-Kr(3)-Kr(2)-Kr(3)-] with Kr(2)-Kr(3) = 4,67(3) Angstrom and Kr(2)-Kr(3)-Kr(2) = 95.6(5)degrees. The charge dipoles induced on the Kr(2) and Kr(3) atoms by their interactions with the zeolite alternate around the rhombus.