Amorphous Nb 3Ge films, which were prepared by d.c. getter sputtering onto a cold (300 K) amorphous SiO 2 substrate, were studied by X-ray scattering. The X-ray diffraction patterns of as-sputtered films, approximately 1 μm thick, exhibited three, broad peaks with no crystalline reflections. Strong, small angle X-ray scattering (SAXS) was observed from these amorphous Nb 3Ge films. The radii of gyration for the scattering regions were obtained from a Guinier plot and found to be 71, 83, 85, 88 and 127 Å, respectively, for an as-sputtered, and then consecutively annealed sample held for 5 h at 550, 620, 690 and 735 °C. The gradient of electron density distribution at the surface of the scattering particle is discussed according to Porod's theory. The X-ray scattering patterns for the sample annealed at 735 °C showed crystalline reflection lines. Detailed examination of the crystalline patterns clearly indicated that most of the sample is of the Nb 5Ge 3 phase. Some extra reflection lines may also be attributed to NbO, GeO 2 and A-15 Nb 3Ge phases. These X-ray results and Rutherford backscattering measurements of 2 MeV 4He ion confirmed that there was a high concentration of oxygen in the sample. Therefore, the observed SAXS suggested that amorphous oxide clusters were the major microstructures in these amorphous Nb 3Ge films. Upon heat treatment, these oxide clusters grew and finally formed crystalline phases. We found that the metastable Nb 3Ge phase has been by-passed, with most of the sample crystallizing in the Nb 5Ge 3 phase.