THE CRYSTAL STRUCTURE OF THE TITLE COMPOUND (SYSTEMATIC NAME: 2-amino-1-methyl-4-oxo-4,5-dihydro-1H-imidazol-3-ium 3-phenyl-prop-2-enoate), C(4)H(8)N(3)O(+)·C(9)H(7)O(2) (-), is stabilized by N-H⋯O hydrogen bonding. Cations are linked to anions to form ion pairs with an R(2) (2)(8) ring motif. These ion pairs are connected through a C(2) (2)(6) chain motif extending along the c axis of the unit cell. This crystal packing is characterized by hydro-phobic layers at x ∼ 1/2 packed between hydro-philic layers at x ∼ 0.