X-ray powder diffraction data, unit-cell parameters and space group for the β-form of pigment yellow 181, C25H21N7O5, are reported [a = 22.556(6) Å, b = 4.9684(9) Å, c = 21.318(6) Å, β = 109.492(4)°, unit-cell volume V = 2252,1 Å3, Z = 4, space group P21/c]. All measured lines were indexed and are consistent with the P21/c space group. No detectable impurities were observed.