Abstract The isothermal change in the electrical resistivity during structural relaxation in the temperature range 500–600 K was measured for amorphous Fe 40Ni 40B 20. The resistivity changes were measured both at the annealing temperature T a and at 77 K. In both cases the resistivity of as-quenched samples decreases continuously with increasing time, but the decrease is smaller by about a factor of 2 when measured at 77 K. The size of the effect measured at 77 K increases with increasing T a, whereas the reverse is true when the effect is measured at T a. Analysis of the data shows that structural relaxation can be separated into two parts: (1) topological short-range ordering (TSRO), the annealing-out of free volume, which can be quantitatively described in terms of a free-volume model with a single activation energy ( E f = 250 kJ mol −1); (2) a “non-TRSO” part, which can be separated into an irreversible contribution and a reversible contribution, which occur simultaneously and cover the same wide range of activation energies (130–250 kJ mol −1). The reversible part is ascribed to chemical short-range ordering (CSRO). An increase in chemical order yields an increase in the resistivity when measured at 77 K and a decrease in the resistivity at T a. In particular, the result that CSRO is accompanied by an irreversible process is new.