St. Louis encephalitis subviral particles, ie, viral ribonucleic acid, were injected intracerebrally into young rats. Characteristic lens cataracts developed during the life span in 86% of the animals injected when 4 days of age. The virus was present in the eye. Cataracts developed subcapsularly starting near the posterior pole of the lens, spreading to the equatorial region, and then over the entire lens leading to a complete white cataract. When the cataract developed early marked microlens, microcornea and microphthalmus were present in adult animals. Infected rats were hypersensitive to touch and neurological changes occurred along with some stunting of growth.