The long-term reduction of intraocular pressure (IOP) resulting from a procedure combining extracapsular cataract extraction and posterior chamber lens implantation with trabeculectomy was compared retrospectively with the IOP-lowering effect of trabeculectomy alone. Forty patients who underwent the combined procedure and 38 who underwent trabeculectomy alone had been followed for an average of 22 +/- 7 months. Both these surgical procedures significantly reduced IOP, but after a year or more, pressure levels were significantly lower in the trabeculectomy group than they were in the combined group: 12.8 +/- 4.2 mm Hg, and 16.5 +/- 5.6 mm Hg, respectively, at 18 months. Also, the mean postoperative fall in IOP was greater in the "filtered" eyes than it was in the combined group (9.8 +/- 4.6 mm Hg and 12.1 +/- 5.2 mm Hg, respectively, at 18 months). Finally, the number of medications required to maintain controlled IOP in the combined group was greater (and resumed preoperative values at 2 years) than it was in the trabeculectomy group (62.5% of the filtered eyes remained controlled unaided).