The reactions of Co‐Mo, Co‐Ta, and Ni‐Ta amorphous films with Si substrates and Al overlayers were analyzed by a combination of backscattering spectrometry, transmission electron microscopy, and x‐ray diffraction measurements. When the alloy is in contact with Si, the reaction temperature lies between 550 and 650 °C and phase separation is generally observed with near noble silicides formed next to the Si substrate and refractory silicides formed on the surface. When the alloy is in contact with Al, the reaction occurs at temperatures of ∼450 °C with a two‐layer structure in the final product. The crystallization temperature of an amorphous alloy is generally higher than its reaction temperature and there is no correlation between the two parameters. The reaction takes place when the annealing temperature reaches the value at which compounds can be formed with both constituents of the alloy.