Enthalpies of formation of binary Laves phases have been critically surveyed and reviewed in this paper. The enthalpy-of-formation data indicate that both geometric and electronic factors are important in stabilizing Laves phases. Analysis of enthalpy data reveals that there are metallic, covalent, and ionic bonds, or a mixed metallic-covalent-ionic bond, in Laves phases. The enthalpies of formation for binary transition-metal lanthanide Laves phases including ReCo2, ReNi2, ReFe2, ReRu2, ReRh2, ReOs2, ReIr2, and RePt2 (Re - lanthanide element), as calculated by the semiempirical Miedema model, are found to be in good agreement with the available experimental data. This indicates that Miedema's theory is capable of predicting the enthalpy of formation of transition-metal lanthanide Laves-phase systems. © 2002 Published by Elsevier Science Ltd.