Recent advances in immunologic technology are making the rapid diagnosis of viral infections of the ocular surface possible. The prompt use of these diagnostic techniques can directly influence therapeutic decision making, such as the use of antiviral drugs and steroids. In this article, existing methods of sampling the ocular surface are discussed, and the yield of infectious virus and viral antigens from various sites on the ocular surface is reviewed. The immunologic principles underlying radio-immunoassays, enzyme immunoassays, and a variety of immunocytologic methods are outlined, along with the advantages and disadvantages of each immunologic technique. In addition to reviewing the methods for detecting viral antigens on the ocular surface, the value of assessing antiviral antibodies in the tear film, as well as prospects for future diagnostic techniques, are discussed.