Purpose: To study the effects of expandable, hydrogel, full-size lenses (FSLs) on lens centration and posterior capsule opacification (PCO) in the rabbit model. Setting: Center for Intraocular Lens Research, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. Methods: Small FSLs designed for human eyes were implanted unilaterally in 20 rabbit eyes. Lens centration and PCO in these eyes were compared with those in eyes with conventional poly(methyl methacrylate) (PMMA) intraocular lenses (IOLs) or aphakia in the fellow eyes. In a second experiment, medium- size or large FSLs designed for rabbit eyes were implanted in 20 rabbit eyes and the results compared with those in eyes with conventional PMMA IOLs. Slitlamp examination of all eyes was performed regularly; after enucleation, gross inspection and microscopic studies were performed. Results: Decentration of FSLs occurred in the presence of an anterior capsule tear or very large capsulorhexis. Posterior capsule opacification developed only at sites where the implanted lens was not in contact with the capsule. Aphakic eyes and looped IOLs developed Soemmering's rings peripherally. In eyes with small FSLs, PCO developed between the lens and the center of the posterior capsule, whereas in eyes with large FSLs, only small amounts of central PCO developed. Retained high-viscosity viscoelastic material had no effect on PCO development.