The change of diamagnetic susceptibility with composition of a number of phases of gamma‐brass structure (Cu&sngbnd;Zn, Cu&sngbnd;Cd, Ag&sngbnd;Zn, Ag&sngbnd;Cd) has been determined. In each case when the phase makes its first appearance with low electron ratio, it is not strongly diamagnetic, but the increase in diamagnetism is approximately lineally dependent on the number of free electrons, and the strongest diamagnetism occurs at the limit of the gamma‐phase with the highest electron ratio possible for the structure.