Beginning in June 1991, we implanted a newly designed, black diaphragm intraocular lens (IOL) into 13 eyes with congenital aniridia after cataract surgery. To the best of our knowledge, this is the first group of patients to receive a black diaphragm IOL. With the first prototype we experienced various difficulties, which prompted four design modifications. The latest IOL with a diaphragm diameter of 10 mm can be guided safely into the ciliary sulcus. IOL implantation improved visual acuity in 9 of 13 eyes; 4 of these exhibited considerably less nystagmus than was observed preoperatively. During the mean follow-up-period of 7.9 months (range, 1-27 months), a slight, persistent intraocular "inflammation" [Tyndall (+)] was observed in all eyes. Glaucoma occurred postoperatively in 4 eyes and was controlled medically in 2 eyes but remained uncontrolled in 2 other eyes that had the condition preoperatively. This pilot study indicates that most patients with congenital aniridia and cataract benefit considerably from the implantation of this newly designed, black diaphragm IOL. However, preexisting glaucoma may herald severe postoperative glaucoma-related problems and should be considered a contraindication until more information has been gained about the long-term tolerance of this IOL.