5-Fluorouracil was used to inhibit experimental intraocular proliferation in rabbit eyes, produced by homologe fibroblast implantation. Two different concentrations were used, 1 and 5 mg in a single intravitreal injection. The eyes were followed up over 4 weeks. Proliferation and resulting traction detachment was reduced from 75% to 30% in the 1-mg 5-fluouracil group. In addition, we observed retinal and vascular changes in a considerable number of eyes treated with 1 mg and much more pronounced alterations in most of the eyes treated with 5 mg fluouracil.