The title compound, 3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazine-hydrogen phthalate-dimethylformamide, C9H8N5Cl2+. C8H5O4-. C3H7NO (lamophthalate), crystallizes in the triclinic space group P1 with unit cell parameters a = 10.1587(6) angstrom, b = 11.3704(7) angstrom, c 12.1976(7) angstrom, alpha = 110.797(1)degrees, beta = 111.61(1)degrees, gamma = 99.53(1)degrees, V = 1151.16(12)angstrom(3), and Z = 2. The asymmetric unit comprises one lamotriginiumcation, one hydrogen phthalate anion, and one dimethylformamide solvate. The dihedral angle between the two planar rings is 65.3(1)degrees. The expected proton transfer occurs at N2 of the triazine ring. Both O-H...O and N-H...O hydrogen bonding stabilizes the crystal structure.