All personnel presumed to have been exposed on the basis of long-standing occupational circumstances to microwaves at the highest levels encountered in a military operational environment were subjected to biomicroscopic examination of the lens. One hundred thirty-five control personnel were also examined along with them, the examiners having no knowledge of the exposure history of any examinee prior to or during the examination. Objective evidence of lens abnormality (opacities, vacuoles, or posterior subcapsular iridescence) was recorded and a statistical comparison made between the two groups on the basis of this evidence. The comparison showed the groups to be essentially the same and did not support the hypothesis that human cataracts are being caused by chronic exposure to microwaves in the military environment in this country.