Correlations between the observed maximum superconducting transition temperature Tc for a given binary alloy system and the alloy melting temperature Tm are pointed out. The stability of alloy phases favorable for high-temperature superconductivity is discussed in terms of alloy phase diagrams. A comparison with the microscopic theory shows that the correlation between Tc and Tm can be interpreted in terms of the d-electron contribution to the cohesive energy of transition-metal alloys as proposed by Bariić, Labbé, and Friedel. The prospects for obtaining high Tc's are discussed in view of these results, and new alloy systems are suggested. © 1975 The American Physical Society.