The best predictor of the extent of eutectic formation between explosive ingredients is the difference between their reciprocal melting temperatures (r(2)=0.838 among 74 examples). Though thermodynamic relationships such as van＇t Hoff＇s equation have come to be recognized in recent years as a basis for predicting eutectic behavior, a quantitative correlation to melting point differences as the major contributor to this behavior seems to have been unrecognized in the energetic materials community. The correlation for binary compositions has the form: In[X(solute)/X(solvent)] = -4077.04 Delta(T-m(-1))-0.0979, where solvent is defined as the lower-melting component. This correlation is derived on the basis of thermodynamic theory with simple approximations.