The change in structure of several amorphous alloys as Fe-P-C, Fe-B, Pd-Si and Pd-Au-Si alloys during isothermal ageing was examined using small angle X-ray scattering measurement and transmission electron microscopy. The SAXS intensity was related to two different types of scattering sources depending on ageing time and temperature. For the as-splatted amorphous alloys and the specimens aged for short period at the temperature below their crystallization temperatures, the week and spreaded SAXS intensity was observed. This indicates the existence of electron density fluctuation in the amorphous state. The average size of their scattering regions was 1.8 to 2.4 nm for Fe-P-C alloys and 1.2 to 0.8 nm for Fe-B alloys. The origin of its fluctuation has been discussed based on one dimensional model. When the amorphous alloys was aged for longer period, the fine crystalline particles precipitate ; those are the two phase lamellar structure of Fe_3P and α Fe for Fe-P-C alloys, the α iron phase for Fe-B alloys and the α phase for Pd-Au-Si alloys, respectively. Their size and structure were determined from the analysis of SAXS intensity and TEM observation
