Gd₃Ru_4+xAll2-x [x = 0.13 (2)], Mr = 1209.44, hexagonal, hP38, P6₃/mmc – kh₂g f ba (No. 194), a = 8.8142 (6), c = 9.5692 (9) A, V= 643.8 (1) A₃, Z = 2, D_x=6.239Mgm ^-3, A(Mo Ka)=0.71073A, u= 20.330 mm^-1, F(000) = 1056 (1), T= 293 K, wR=0.023 for 338 contributing unique reflections. Gd₃Ru₄AI₁₂ is a substitution variant of the Sc₃Ni_{11Ge4 structure which is a partly disordered variant of the Sc3Ni11Si4 type, all three structures being ternary substitution derivatives of the EuMg5.2 or ErZn5 types. Contrary to the related structure types, in Gd3Ru4AI12 both Wyckoff sites 2(a) and 2(b) have full occupation, i.e. an ordered arrange- ment of alternate Ru and AI atoms is observed along the c axis. The structure of Gd3Ru4AI12 is built up of two kinds of layers perpendicular to [001]: planar layers of composition Gd3Al4 and puckered layers of composition Ru4AI5. Similar layers are found in cubic Hf6Ni7AI16, a ternary substitution variant of Th6Mn23, as well as in hexagonal Sr9Mg38 and BaLi4.}