The loss of lens transparency underlying cataract is widely attributed to a loss of crystallin protein stability and their subsequent propensity to partially unfold, leading to aggregation and precipitation. This process of destabilisation appears to arise due to cumulative post-translational modifications, e.g. deamidation, oxidation, glycation and truncation, of the lifelong crystallin proteins. Here we have investigated the stability, structure and aggregation propensity of two variants of human γS-crystallin identified in aged lenses: (i) N143D, the most common product of deamidation, and (ii) S167X, a common C-terminal truncation. The potential contribution of these variants to the development of age-related cataract is discussed.