We compared the effects of Viscoat and Healon on postoperative increases in intraocular pressure in patients undergoing uncomplicated extracapsular cataract extraction with posterior chamber intraocular lens implantation in a prospective, randomized, single-masked study. Eleven eyes received Viscoat and 13 received Healon. The Viscoat or Healon was aspirated from the anterior chamber with the irrigation-aspiration tip of an automated irrigation-aspiration system at the end of the procedure. No prophylactic intraoperative or postoperative ocular hypotensive agents were used. Intraocular pressure was measured at three, six, 12, and 24 hours postoperatively. Compared with preoperative intraocular pressure, postoperative intraocular pressure was significantly increased in both the Viscoat group and the Healon group. Some postoperative intraocular pressures were as high as 50 to 60 mm Hg, despite removal of the viscoelastic substance at the end of surgery. There was no significant difference in the postoperative intraocular pressures of the Viscoat group and the Healon group.