Background and Objective: To investigate the effectiveness of various implants used in experimental deep sclerectomy and to report tissue reactions developed to these implants histopathologically. Materials and Methods: Forty eyes of 40 New Zealand white albino rabbits underwent deep sclerectomy with various implants. The rabbits were divided into four groups; each consisted of 10 eyes. Deep sclerectomy was performed using copolymer materials in group 1, silicone materials in group 2 and chromic catgut suture in group 3. No implants were used in the control group ( group 4). Clinical and histopathological examinations were performed to investigate the effectiveness of implants. Results: Mean preoperative intraocular pressure (IOP) was 14.4 +/- 1.6 mm Hg in group 1, 14.5 +/- 1.8 mm Hg in group 2, 13.8 +/- 1.5 mm Hg in group 3 and 14.5 +/- 1.2 mm Hg in group 4. The final postoperative IOPs were 10.7 +/- 0.9, 10.6 +/- 0.8, 13.5 +/- 1.0, and 14.5 +/- 1.4 mm Hg, respectively. At 2 months, the decrease in IOPs from baseline and the persistence of the filtering bleb were significantly marked in group 1 and group 2 (p < 0.001). Histopathological evaluation revealed that copolymer and silicone materials formed a smooth and regular intrascleral space. There were no foreign body reaction, tissue destruction or fibrosis in group 1 and group 2, but chromic catgut sutures caused severe fibrosis and inflammatory reaction in group 3. Mean histopathologic score of group 1, group 2, group 3 and group 4 was 0.7 +/- 0.5, 0.8 +/- 0.5, 2.4 +/- 0.6, and 0.1 +/- 0.3, respectively. Conclusion: Copolymer or silicone materials may increase the success rate of surgery by maintenance of a large and regular intrascleral space after deep sclerectomy and prevention of collapse of the flap. Copyright (C) 2004 S. Karger AG, Basel.