Mg65Cu25Y10 ribbons were produced by melt spinning. Their microstructure was investigated in its as-cast condition, after pressing under 0.5 GPa for 5 min under different temperatures -RT, 50, 100, 150, and 200• C -and after five-minute exposure to the above temperatures without pressing. The microstructure was characterized by means of XRD, DSC, HRSEM, and HRTEM. XRD and DSC studies showed that the as-cast material had an amorphous character and that the material crystallized during exposure to temperature with or without applying stress. HRTEM revealed that the as-cast Mg65Cu25Y10, although known to be one of the best glass formers, is nano-crystalline rather than amorphous.K e y w o r d s : microstructure, melt spinning, metallic glass, Mg65Cu25Y10