This is a review of the current status of clinical research on the prevention of posterior capsular opacification (PCO), which is now the commonest complication of cataract surgery occurring in up to 50% of patients by 2 to 3 years after the operation. PCO is caused by lens epithelial cells retained in the capsular bag following surgery which then proliferate, migrate and transform to myofibroblasts. Interest in the prevention of PCO has centred around surgical technique, pharmacological methods to remove or destroy lens epithelial cells and changes in intraocular lens material and design. Changes in surgical technique have little effect in prevention of PCO although a capsulorhexis size which lies on the optic diameter appears to be beneficial. Many different cytotoxic drugs and pharmacological agents have been used experimentally to prevent PCO but the problem has limited damage only to lens epithelial cells. So far, no method has been shown to be safe for clinical use. Current interest is centred once again on the intraocular lens itself, particularly the material that it is made from and changes in its edge profile.