Flexible silicone posterior chamber intraocular lenses made of a proprietary formulation were implanted in rabbits following planned extracapsular lens extraction. The lenses were of three designs: unfenestrated, partially fenestrated, and fully fenestrated haptics. Biostability and tissue reactivity of the silicone lenses and another manufacturer's polymethylmethacrylate lenses appeared equivalent as evaluated clinically by slitlamp biomicroscopy and by light microscopy. The frequency and distribution of lens precipitates were evaluated grossly and by scanning electron microscopy and appeared notably less prominent on the surfaces of the hydrophobic silicone lenses.