The development of a simple, sensitive and reliable enzyme-linked immunosorbent assay (ELISA) for the exact titration of herpes simplex virus type 1 -- and type 2 -- specific antibodies in human serum has made it possible to perform large serological HSV type-specific diagnosis of clinical cases of post and present genital HSV infections. The distribution of HSV type-specific IgG antibody in 473 sera from women with a first episode of symptomatic genital herpes (group A), 602 sera from women with a previous history of symptomatic genital herpes (group B) and 945 sera from non-selected adult Danes (controls, group C) gave the following results: 34 percent of the women in group B had antibodies only to HSV type compared to 6 and 4 percent in group A and C respectively. 64 percent of women in group A were sero-negative, while only 9 and 18 percent sero-negative were found in group B and C respectively. A majority of the sero-negative in group A seroconverted. One third developed antibodies to HSV type 1 and two thirds to HSV type 2.