A prospective study of the effect of cataract extraction andintraocular lens implantation on insulin-dependent diabetics is presented. Cataract extraction was performed on 138 patients with diabetic retinopathy. The patients were randomly selected for intracapsular or extracapsular extraction and for the administration of topical indomethacin or placebo. In a second group, 103 diabetic patients received intraocular lens implants, which were anterior-chamber-angle fixated, iris supported, iridociliary sulcus supported, or placed in the capsular bag. Random selection determined who among the extracapsular cases would have on-the-table capsulotomy or six-month-postoperative capsulotomy. The study indicated that a greater progression of diabetic changes occurred in both the posterior and the anterior segment of the eye after intracapsular extraction than after extracapsular extraction, especially if the capsulotomy was performed six months postoperatively. Furthermore, the study indicated that in-the-bag implantation without on-the-table capsulotomy was a safe procedure; anterior-chamber-angle-fixated lenses exhibited a higher incidence of diabetic changes in the anterior and posterior segments than the other lenses.