The humoral immune response to HSV-1 and HSV-2 proteins was examined in patients with primary first-episode genital herpes. Ten patients had culture-proven HSV-1 infections, 37 had HSV-2 infections, and all were seronegative to HSV proteins before developing their infections. Development of serum antibodies to individual HSV proteins and glycoproteins was determined by immunoprecipitation of radiolabeled HSV-1- and HSV-2-infected cell proteins and subsequent gel electrophoresis. In HSV-1 patients, a sequential development of antibodies to HSV-1 proteins was observed with early appearance of antibodies to the nucleocapsid protein p148 and to glycoproteins gB and gC. Seroconversion to gD and to a polypeptide of 88,000 molecular weight (p88) occurred next, and, finally, seroconversion to gE and to a nonglycosylated 66,000 dalton protein p66. In HSV-2 patients, antibodies to HSV-2 proteins p148, gB, and p88 appeared within 1 week of onset of symptoms. Seroconversion to p66, gD, and to a complex of glycoproteins gC and gE ("g80") occurred later, at a mean time of approximately 3 weeks. Seroconversion to HSV-1 gB, p88, and p66 occurred significantly later than seroconversion to the homologous counterparts. Seroconversion within 21 days of onset to HSV-2 gD, g80, and p66 was associated with a longer time to the first recurrence in HSV-2 patients, suggesting a possible role of these antibodies, alone or in combination, in the maintenance of HSV-2 latency in humans.