alphaB-crystallin acts as an anti-apoptosis protein in human lens epithelial (HLE) cells. We recently identified a missense mutation in alphaB-crystallin that changes proline 20 to an arginine (P20R) in a Chinese family with autosomal dominant congenital posterior polar cataract. The impact of the P20R mutation on the anti-apoptosis function remains unclear. To explore the anti-apoptotic activity of alphaB-crystallin wild type (alphaB-wt) and its P20R mutant under oxidative stress, HLE cells were transfected with alphaB-wt and alphaB-P20R constructs and expression was measured by western blotting. Flow cytometry and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP digoxigenin nick end-labelling (TUNEL) staining were performed to investigate apoptosis. We found that alphaB-wt performed a dominant role in inhibiting stress-induced apoptosis, but this function was impeded in cells expressing alphaB-P20R. The P20R mutant of alphaB-crystallin exhibits diminished anti-apoptotic activity compared with the native protein.