The two following salts have been prepared [(CH 3 ) 2 C(NH 3 )-COOH] + · H 2 P04 (aMADP) and [CH 3 CH 2 CH(NH 3 )COOH] + · H 2 PC>4 (L0MADP). The crystal parameters are: a = 10.060(2), b = 7.634(2), c = 5.852(2) Ä, α = 97.32°(5), β = 107.50°(5), y = 81.16°(5); Z=2; Pi for aMADP and a = 7.164(2), b = 6.533(2), c = 9.458(2) Α; β = 105.48°(7); Ζ = 2; P2i for L/?MADP. Crystal structures were solved by direct methods and refined to a final R value 0.026 with 2889 independent data for aMADP and to R = 0.033 with 2027 reflexions for L/JMADP. Hydrogen atoms located by difference-Fourier syntheses were refined. The layer structure of aMADP and the chain structure of L/?MADP emphasize the importance of H2PO4 polymeric anion and its possible use in the design of polar inorganic materials. The effect of chirality on the anion-aggregation, through the hydrogen bonds, clearly indicated by the L/JMADP structure and some others already described, may be easily transposed to individual, cylic, chain or layer inorganic oxoanions.