An extracapsular cataract extraction was performed on both eyes of 24 rabbits. Irrigation for 10 min of the capsular bag of the left (test) eye with 8–12 cm³ of 1 litre of BSS-plus® to which had been added 50 mg of 5-fluorouracil significantly inhibited proliferation of the anterior capsular epithelium as compared with the right (control) eyes identically treated except for the omission of 5-fluorouracil (p < 0.001). Corneal endothelial counts did not differ significantly. A reduction in opacification of the posterior capsule is expected from 5-fluorouracil treatment.