Six cases representing different stages of cataract formation secondary to eye trauma were subjected to quantitative microradiographic or electron microscopic examination. Anterior and posterior subcapsular cataracts were found to contain extensively swollen lens fibers in the subcapsular cortex. Microradiographic measurements revealed a reduced concentration of dry mass in the subcapsular cortex around the whole circumference of the lens. The inner cortex and the nucleus appeared normal both microradiographically and electron-microscopically. Two of the examined cases had an opaque-cataract membrane and one had a Soemmerring's ring. The opaque membranes consisted of irregular masse of degenerated lens fiber material as well as regenerated lens epithelial cells. A wide range of dry mass concentration was found in the opaque membrane that was studied microradiographically. Alterations in morphology and dry mass concentration are more than sufficient to explain the development of opacification in traumatic cataract.