Partial isothermal sections of the Al–Pd–Ru phase diagram at 790 and 900°C are presented. Complex orthorhombic ɛ-phases extending from Al 3 Pd up to 15at.% Ru exhibit structural variants including transient irregular structures. The Al 3 Pd 2 phase dissolves up to 2at.% Ru, Al 13 Ru 4 <2.5at.% Pd and Al 2 Ru up to 1at.% Pd. A stable icosahedral quasicrystalline phase is formed around the Al 71.5 Pd 17 Ru 12.5 composition. At nearby compositions two complex primitive cubic phases with a≈2.0 and ≈4.0nm were observed. These cubic phases exhibit powder X-ray diffraction (XRD) patterns very similar to that of the icosahedral phase. At compositions close to the high-Ru limit of the ɛ-range the electron diffraction patterns of complex orthorhombic structures and 1D quasicrystalline structure were revealed. At lower-Al concentrations three ternary cubic phases structurally related to quasicrystals are formed: primitive C (a≈0.75nm), bcc C 1 and fcc C 2 with a double lattice parameter.