[en] Large crystals of triclinic barium dihydrogen phosphate, Ba(H₂PO₄)₂, were grown in a highly acidic solution of phosphoric acid, barium oxide and water. These crystals were irradiated for 12 hours with ⁶⁰Co gamma radiation and electron paramagnetic resonance spectra (9 GHz) were recorded, all at 77⁰K. The x laboratory axis was colinear with the crystalline asis a. The b axis was in the xz plane 19.5⁰ from the z-axis. The spectra indicated the presence of hydrogen (g = 2.0011 a = 509.5 G) and H₂PO₄ radicals. The H₂PO₄ spectrum split into two similar spectra separated by about 1 Gauss with g = (2.0017 2.0234 2.0144) and (2.0040 2.0235 2.0124) and a = (38.0 35.9 34.8) and (37.8 35.9 35.0) G respectively. These two spectra are due either to the less distorted PO₄^2- radical in the structure, damaged in different ways by the irradiation, or to normally equivalent tetrahedra becoming inequivalent due to an antiferroelectric transition at 133 K. Each line of the H₂PO₄ spectrum had two satellite lines. Their spacing from the main line varied with the dc field and was approximately equal to the proton resonance frequency in the dc field. These lines are due to matrix or environmental hydrogen atoms