Abstract : Rabbit eyes were irradiated utilizing qualitative and quantitative control of the microwave energy entering the eye. In all cases, the left eye was exposed to either pulsed or continuous wave emission at 5400 megacycles (megahertz) per second and the right eye served as an unexposed control. During the month following irradiation, the eyes were examined for evidence of lenticular opacification. The lens changes induced by acute exposure to 5400 MC were found to be directly related to average power irrespective of the wave form, whether continuous or pulsed, and, in the latter instance, irrespective of peak power or pulse duration. Irreversible opacification in the lens was required as an end point. The results of lens injury are plotted in dashed line for exposures at 5400 MC and compared to previous data plotted in solid line for exposures at 5500 MC on the following graph.