It has been known for many years that some of those infected with herpes simplex virus infection were asymptomatic, however the inability of antibody tests to reliably distinguish between antibodies to HSV-1 and HSV-2 made it difficult to determine the relative extent and importance of asymptomatic and symptomatic infection. Recently, commercially available type-specific assays that can distinguish between antibodies to the two virus types have become available. These tests not only make it possible to better define infection in symptomatic patients and their sexual partners but also to identify individuals without symptoms. In this talk I will discuss the role of these assays in determining the pattern and distribution of infection in different populations around the world. In addition I will discuss the possible uses for these tests in clinical practice as well the potential advantages and disadvantages of using these tests for screening for infection in the wider population.