The diffusion-multiple approach can be used to map phase diagrams at an efficiency orders of magnitude faster than the conventional equilibrated alloy method. This paper addresses a concern about the reliability of the results, especially whether the data obtained from diffusion multiples can produce reliable equilibrium phase diagrams. The following topics will be discussed: (a) establishment of local equilibrium at the phase interfaces, (b) X-ray interaction volume vs. thickness of the phases ( microprobe related issues), (c) reliability of phase diagrams from equilibrated alloys, (d) usefulness of electron backscatter diffraction, (e) impurity-induced stabilization of metastable phases, and, (f) missing phase situations. A direct comparison of several ternary systems obtained from both diffusion multiples and equilibrated alloys was made. The good agreement between them clearly demonstrates the reliability of phase diagrams determined from diffusion multiples. (C) 2004 Kluwer Academic Publishers.