This randomized study of 100 patients compared the effects of two viscoelastic agents on intraocular pressure after phacoemulsification cataract extraction with intraocular lens implantation. In 50 patients, sodium hyaluronate was instilled in the anterior chamber before lens insertion and then evacuated. Sodium chondroitin sulfate-sodium hyaluronate was instilled in another 50 patients and was not evacuated. Postoperative intraocular pressure increases occurred much less frequently (6% versus 54%) and were milder in the group that received sodium chondroitin sulfate-sodium hyaluronate. Mean peak intraocular pressure was reached at 16 hours in both groups; peak pressure was 31.7% higher in the group that received sodium hyaluronate. Better clearance from the eye due to the lower molecular weight of sodium chondroitin sulfate-sodium hyaluronate may explain the differences in intraocular pressures between the groups.