OBJECTIVE To compare the hypotensive effect in normal eyes of three formulations with different concentrations of brimonidine tartrate: 0.2%; 0.15% and 0.1%. METHODS Prospective, randomized, double-blind study included 60 volunteers, who underwent initial ophthalmologic examination and measurement of intraocular pressure (IOP). Individuals were divided into three groups: (1) brimonidine tartrate 0.15%, (2) brimonidine tartrate 0.2% and (3) brimonidine tartrate 0.1% and randomly received one drop each of drops in each eye. The IOP was measured after 30 minutes, 1 hour and 2 hours. RESULTS We found that all concentrations of brimonidine tartrate significantly reduced intraocular pressure during the study period, with p<0.05. When analyzing the percentage difference of the hypotensive effect of each group, we found no significant difference between the studied groups: (1) -13.50%, (2) -11.50%, (3) -11.90% after 30 minutes (p=0.650); (1) -24.30%, (2) -18.60%, (3) -18.30% after 1 hour (p=0.324); (1) -29.14%, (2) -21.20%, (3) -25.60% after 2 hours (p=0.068). CONCLUSIONS There is no statistically significant difference in intraocular pressure reduction (peak period) between the three formulations of brimonidine.