Data obtained from a series of differential thermal analysis studies have been used, along with x ‐ray and electron beam microprobe analyses, and a regular solution interpolation procedure to construct a major part of the equilibrium ternary liquidus ‐solidus phase diagrams of the Ga ‐As ‐Cu, Ga ‐As ‐Ag, and Ga ‐As ‐Au systems. In these systems the primary phase field occupies a major part of the phase diagram.