Crude antigenic preparations made from rabbit cornea cells infected with either HSV type 1 or type 2 could be used in ELISA for titration of HSV type-specific antibodies in human sera. After immunochemical binding of the crude HSV antigens in microtitre wells by use of type-homologous rabbit antibodies, type-common antigenic sties were blocked with type-heterologous rabbit antibodies. Titration of human sera in this system showed that high concentrations of type heterologous rabbit antibodies were capable of completely blocking type-common antigenic sites, while leaving type-specific antigenic sites unblocked and capable of reacting with human antibodies. Thus HSV type-specific antibodies in human sera could be measured in ELISA without the use of purified typespecific antigens.