We prospectively evaluated the efficacy and safety of the twice-daily application of 1% ALO 2145 (p-aminoclonidine hydrochloride, a topical alpha 2-agonist) in 21 normal volunteers for one month. Criteria measured included intraocular pressure (IOP), basal tear secretion, pupillary size, corneal sensitivity, heart rate, and blood pressure; urinalysis and blood chemistry studies were also performed. The mean (+/- SD) IOP fell 38.7%, from 17.5 +/- 3.9 mm Hg to 10.7 +/- 3.4 mm Hg, in five hours. The mean IOP remained between 23% and 30% below the pretreatment level when checked 12 hours after the last drop's instillation from day 8 through day 28 of the study. No clinically significant changes in mean systolic blood pressure, blood chemistry values, urinalysis results, basal tear secretion, or corneal sensitivity were noted. The mean heart rate and diastolic blood pressure were each significantly decreased at only one of nine time intervals. Dry mouth was noted at some time in 52% of volunteers. ALO 2145 seems to be effective in lowering IOP in normal volunteers, without marked cardiovascular effects.