1,2-Ethylenediphosphonic acid reacts with gallium nitrate in water to give new pillared layered gallium phosphonates, the structure of which depends on the experimental conditions used for their preparation. Thus, Ga-4(O3PC2H4PO3)(3) (1) and Ga-2(OH)(2)(O3PC2H4PO3) (2) were isolated and the structure of I was solved by single-crystal X-ray diffraction. while 2 was shown to have the same metal/PO3 arrangement as the previously described Ga(OH)(O3PCH3). Ga-4(O3PC2H4PO3)(3) (1) is triclinic, with space group P (1) over bar with Z = 2, a = 5.1480(4), b = 8.0354(7). and c = 12.383(1) Angstrom. alpha = 91.34(1), beta = 101.40(1), and gamma = 90.86(1)degrees; V = 501.9(1) Angstrom (3). The structure of I is unusual with (i) mixed GaO4 and GaO5 Sites while a 6-fold coordination is observed for gallium in (2) and (ii) the presence of the organic moiety within both the layers and the interlayer space. The two compounds were fully characterized using P-31 and Ga-71 solid-state NMR.