Abstract Shear zones that have widened with time can display margin-to-interior microstructural profiles unlike the real microstructural history of the interior rocks. Shear zones that have not widened with time can provide more reliable views of microstructural history, and therefore of deformation processes. Even the latter zones can mislead, however, where there has been an annealing overprint during or following the shearing interval. These sources of uncertainty need to be acknowledged more regularly, and if possible eliminated, by workers interpreting deformation processes from shear-zone strain gradients.