The authors report on 72 cataract extractions following filtering procedures for glaucoma. In 45 cases they performed a purely corneal incision in the upper part of the globe (in 17 cases the classical von Graefe knife incision was used; in 28 cases a three-plane incision ab externo using a razor blade and scissors was done). In the other 27 cases the globe was opened from the outer surface by performing a corneoscleral incision with a limbus-based conjunctival flap. With regard to postoperative intraocular pressure and intraoperative and postoperative complications the two techniques - the ab interno incision and the ab externo incision - produced equally good results. Moreover, a slightly higher residual astigmatism was observed after the purely corneal incisions. The advantages and disadvantages of the two techniques for opening the globe following a filtering procedure for glaucoma are discussed. Finally the authors describe the procedure they currently use, depending on the preoperative situs.