Intraocular pressure alteration after ruby laser irradiation of rabbit irises was studied using tonometric and manometric methods. These results were compared to those alterations caused by mechanical stimulation with a needle. Following ruby laser impact, the intraocular pressure initially elevated and then decreased before returning to normal. This pattern was found to be similar to the one caused by mechanical stimulation. Topically administered epinephrine suppressed the pressure elevation caused by the ruby laser irradiation. The pressure elevation is thought to be of vascular origin.