Most posterior chamber intraocular lenses (IOLs) in common use today measure 13.5 mm to 14.0 mm in diameter. Some investigators recommend using smaller lenses (e.g., 12.0 mm to 12.5 mm). To investigate the effect of smaller lenses, experimental phacoemulsification procedures were performed in 16 eyes of white rabbits using two intraocular lens sizes: 14.0 mm and 12.5 mm. Each lens was evaluated for its effects on posterior capsule opacification and optic decentration, two of the most common complications of modern cataract surgery and intraocular lens implantation. The 12.5 mm lens showed a slightly smaller amount of decentration than the larger lens and a comparable amount of posterior capsule opacification.