The problem of the discrepancy between the activation energies for diffusion and the activation energy for the Zener relaxation in substitutional solid solutions is examined for the case of dilute alloys. Using single crystals of αAg-Zn alloys it has been possible to obtain (by extrapolation) a value Qr = 39.0 kcal/mole for the activation energy for relaxation in alloys approaching infinite dilution. This value is distinctly below the activation energies for diffusion of Zn and of Ag into pure silver. The interpretation of these three activation energies and the reasons why they differ are much more apparent for the dilute alloys than for the concentrated alloys previously studied. Specifically, Qr is the activation energy involved in the reorientation of a Zn-Zn pair, while the tracer measurements relate to the jump of isolated Zn and Ag atoms, respectively. The orientation dependence of the relaxation time in single crystals of the 26 at. % Zn alloy was also measured. The results show that the relaxation time is very nearly independent of orientation. © 1964.