PURPOSE. To describe a new model of posterior capsule opacification (PCO) in rodents METHODS. An extracapsular lens extraction (ECLE), by continuous curvilinear capsulorrhexis and hydrodissection, was performed in 42 consecutive Brown Norway rats. Animals were killed at 0, 6, and 24 hours and 3, 7, and 14 days after surgery. Eyes were enucleated and processed for light microscopy and immunohistochemistry. RESULTS. In 34 (81%) of the animals the operated eye appeared well healed before death, with a clear cornea and a well-formed anterior chamber. In eight (19%) there was no view of anterior segment structures because of hyphema, fibrin, or corneal opacification. PCO was clinically evident 3 days after ECLE and was present in all animals at 2 weeks. Immediately after ECLE, lens epithelial cells (LECs) were present in the inner surface of the anterior capsule and lens bow. Twenty-four hours after surgery, LECs started to migrate toward the center of the posterior capsule. At 3 days, multilayered LECs, some spindle shaped, were present throughout the lens capsule. Capsular wrinkling was apparent. Lens fibers and Soemmering's ring were observed in all animals 14 days after surgery, indicating some degree of cellular differentiation. Activated macrophages were present in greater numbers at 3 and 14 days after surgery (P <0.05), when proliferation and migration of LECs appeared to be greatest, and lens fiber differentiation was evident, respectively. CONCLUSIONS. In rodents PCO occurs after ECLE and is associated with low-grade inflammation, mostly of mononuclear macrophages. Although no intraocular lens implantation was performed, this model appears to be valuable for studying the sequence of events that leads to PCO after cataract surgery and the extracellular matrix cues that promote lens fiber differentiation.