Specular microscopy was performed before cataract surgery in approximately 3,500 patients. In 127 cases (approx. 4%), implantation of an intraocular lens (IOL) did not appear appropriate, in view of the condition of the cornea. Many of these patients had additional ocular pathology, such as retinal detachment, glaucoma, and intraocular inflammation. In 40 of the patients, IOLs were implanted in spite of the results of specular microscopy, while 48 patients underwent surgery without lens implantation. The incidence of postoperative corneal complications in the two groups was the same. The main problems were caused by cell polymorphism and severe cornea guttata. It is extremely difficult to assess cell polymorphism at the slitlamp. Especially in patients with other ocular diseases and corneal lesions visible at the slitlamp, it is recommended that specular microscopy be performed prior to cataract surgery with implantation of an IOL.