A micro solid phase radioimmunometric assay has been developed which measures type-specific antibody in human sera to herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2). The test is performed by coating wells of microtiter plates with purified HSV-specified glycoproteins, VP123 and VP119, derived from HSV-1- and HSV-2-infected cells, respectively. The coated wells are then incubated with diluted unadsorbed sera and subsequently with radio-iodinated goat anti-human IgG reagent. Because these major viral envelope glycoproteins contain type-specific antigenic determinants, type-specific antibodies are preferentially detected in our assay.