One of the complications after implantation of posterior chamber intraocular lenses is fibrin reaction. The authors analyse group of 653 patients--659 eyes after the operation of cataract with implantation of posterior chamber IOL operated in 1991-1992 at Postgraduate School of Medicine, Ophthalmology Department in Bratislava. The fibrin reaction was found out in 33 cases (5%). This reaction started between the first and third day after the operation. From this group of 33 patients, 14 (43%) were treated for glaucoma, 11 (33%) had diabetes mellitus and 3 (9%) overcome uveitis in past years. In all cases after the treatment came to the complete loss of fibrin. Finally visual acuity was 5/5 to 5/10.