A high incidence of keratoconjunctivitis was observed in a closed colony of inbred Lewis/Wistar rats. Clinical signs including blinking, ocular discharge, circumcorneal flush, corneal opacity, ulceration, pannus, hypopyon, and hyphema were observed at .apprx. 3 wk of age. Acute disease subsided by 6 wk, but some lesions progressed to low-grade chronic keratitis. Of the affected rats, 6% developed megaloglobus, which usually appeared by 3 wk of age. Lesions included focal or diffuse interstitial keratitis, corneal ulceration, anterior synechia and inflammatory exudate in the anterior chamber. A high incidence of lenticular and retinal degeneration was associated with megaloglobus. Most affected rats also had harderian dacryodenitis. Sialodacryoadenitis virus (SDA) was recovered from nasal washes, but not from affected eyes. Serological evidence indicated tha SDA virus infection was widespread in the colony.