X-ray cataracts in rats were shown in an earlier paper to be enhanced by a unilateral common carotid ligature. It was the aim of the present paper to investigate lens wet weights, protein concentrations and several specific enzyme activities in the lenses of these animals. Irradiated lenses weighed less than controls. Carotid ligatures further reduced wet weight only after previous X-irradiation. Protein concentrations were slightly reduced in irradiated lenses and it appeared that opacification was accompanied by diminished protein synthesis and growth rate. Few changes of specific enzyme activities were noted and they are probably indirect consequences of the radiation injury.