The intraocular pressure (IOP) of glaucomatocyclitic crisis with the attack fell 50.3%, from 37.8 ± 8.2 mmHg to 18.8 ± 4.8 mmHg, 4 hours after instillation of 1% apraclonidine. Glaucomatocyclitic crisis showed a more significant hypotensive response to 1% apraclonidine than primary open-angle glaucoma (24.8%, from 43. 1 ± 8.1 mmHg to 32.4 ± 7.5 mmHg after 4 hours). The intraocular pressure decrease percentage was similar regardless of the initial level of intraocular pressure. Clinically significant changes in mean systolic and diastolic blood pressures, were not observed, however, a mild decrease in the pulse rate was noted. And the local mydriatic effect on the pupillary diameter was significant. Apraclonidine, 1% might be newly indicated to control the IOP rise of glaucomatocyclitic crisis. Further studies on the possible mechanism of the prostaglandin mediated hypotensive effect of 1% apraclonidine are suggested.