An outbreak of severe conjunctivitis involved approximately 30% of a dairy herd of 118 cattle. Infectious Bovine Rhinotracheitis (IBR) virus was identified by cytopathic effects and fluorescent antibody techniques from conjunctival swabs of affected animals. The disease typically presented as a unilateral ocular disease with systemic signs of pyrexia, inappetance, decreased milk production, and some subsequent abortions.