Recent data on subgrain size and spacing gradients in the Cu‐Ni system allow a more critical examination of a technique currently used to obtain the composition profiles of small diffusion zones. These data support the assumption that the broadening from individual subgrains need not include a spacing gradient term when volume diffusion is predominant. However, care should be taken in the interpretation of the earliest stage of diffusion where grain boundaries, surface, and other defects may introduce large spacing gradients.