Thirty-two eyes of 32 patients were treated with 0.5% timolol, 2% pilocarpine, or normal saline five and 30 minutes following neodymium-YAG laser posterior capsulotomy in a randomized, double-masked study. Mean maximum intraocular pressure (IOP) elevation was 8 +/- 2 mm Hg following treatment with normal saline, 5 +/- 3 mm Hg following treatment with 2% pilocarpine, and 1 +/- 2 mm Hg following treatment with 0.5% timolol. Fewer patients treated with 0.5% timolol developed an IOP elevation of 5 mm Hg or more than control patients. On aphakic patient treated with 0.5% timolol developed a maximum IOP greater than or equal to 40 mm Hg. We found that treatment with 0.5% timolol after neodymium-YAG laser posterior capsulotomy provides partial protection from IOP elevation.