PURPOSE: To study the association between after-cataract and secondary glaucoma after lensectomy and 5-fluorouracil treatment in an experimental infant rabbit model. SETTING: St Erik Eye Hospital, Karolinska Institute, Stockholm, Sweden. METHODS: Lensectomy was performed in both eyes of 16 3-week-old rabbits. One randomly selected eye in each rabbit was injected with 2.5 mg of 5-fluorouracil (5-FU) at surgery and 5.0 mg the day after surgery to reduce the formation of after-cataract. Axial length, corneal thickness, corneal diameter, and intraocular pressure were measured preoperatively and 4 times during the 6 months following surgery. Six months after surgery, the wet weight of the after-cataract was determined. RESULTS: In 16 aphakic eyes treated with 5-FU, no or a minimal amount (0.10 g); 8 of these developed glaucoma. The other 6 eyes had no or minimal after-cataract and did not develop secondary glaucoma. The relationship between after-cataract and secondary glaucoma was statistically significant. CONCLUSION: A significant relationship between the amount of after-cataract and the development of secondary glaucoma was found in aphakic infant rabbit eyes.