A prospective, randomized, double-masked study compared topical 1% ALO 2145, an alpha 2-agonist, with placebo in therapy for immediate postoperative intraocular pressure (IOP) rise after argon laser trabeculoplasty. Seventy-three eyes (73 patients) underwent 360 degrees of treatment utilizing 80 spots of 800 to 1000 mW of power. Intraocular pressure rise was measured hourly for the first three hours after operation, at one week, and at one month. Eyes treated with ALO 2145 had both significantly lower mean IOPs and greater IOP decreases from baseline than placebo-treated eyes during the first three hours after operation. No eyes treated with ALO 2145 and six eyes (18%) treated with placebo experienced an IOP rise of 10 mm Hg or greater. Twenty eyes (59%) in the placebo group and eight eyes (21%) treated with ALO 2145 had an IOP elevation. No change was detected in the mean heart rate. ALO 2145 appears to be effective in eliminating large, acute IOP elevations after argon laser trabeculoplasty.