We have examined the equilibrium surface composition of two very dilute Fe–Zr binary alloys: Zr–0.05‐at. %‐Fe and Fe–0.06‐at. %‐Zr. We find that reversal of the segregating element occurs in the respective dilute limits. Iron segregates to the surface of the zirconium rich alloy, while zirconium segregates to the surface of the iron rich alloy. Segregation of iron to the surface of the zirconium rich alloy was reversible for T≳970 K with a heat of segregation of 71.1±8 kJ/mole. Segregation of zirconium to the surface of the iron rich alloy was large and not reversible. The observed behavior is discussed in light of two widely used models of surface segregation.