ABSTRACTWe have used fluctuation electron microscopy (FEM) to measure nanoscale mediumrange order in amorphous Al₉₂Sm₈. Samples of this amorphous alloy formed by rapid quenching (melt-spinning) show a high density of pure Al nanocrystals (>10²⁰ m^-3) after low temperature (< 250 °C) devitrification. In samples amorphized by deformation (cold-rolling), primary Al-crystallization does not occur. This difference in devitrification behavior suggests an underlying structural difference in the amorphous state. FEM is a quantitative microscopy technique for determining nanoscale medium-range order in amorphous materials. Our measurements show that amorphous alloys formed by melt-spinning and cold-rolling have significant structural differences, and that annealing melt-spun alloy under conditions previously shown to modify the devitrification thermodynamics also changes the medium-range structure.