Recent evidence indicates that many of the characteristics of herpes simplex virus (HSV) ocular disease are determined by the genome of the virus strain. The type and severity of epithelial disease, as well as the morphology of the lesions, have been demonstrated to be genetically controlled, and the region of the viral DNA responsible for these aspects of the disease has been identified. In addition, the frequency of reactivation of the latent virus may be inherent in the genetic makeup of the virus, although host factors appear to influence the appearance of frank disease. Drugs for the treatment of epithelial herpes inhibit virus replication in the host cells; the newest and most effective drug, trifluridine, heals 97% of epithelial lesions within two weeks. The place of thymidine kinase selective drugs in ophthalmology has not been determined. There are, as yet, no drugs specific for stromal herpes, and no drugs have been shown to eradicate the latent virus from the ganglia or to prevent the recurrence of ocular herpetic disease.