Acute serum samples from patients with nonprimary first-episode genital herpes were evaluated for the presence of type-specific antibody to herpes simplex virus type 1 and type 2. A standard microneutralization assay and western blot analysis, which identified the response to individual polypeptides of type 1 and type 2 herpes, were performed in both unadsorbed serum samples and serum samples adsorbed with either type 1 or type 2 antigens to remove cross-reacting antibodies. Of 24 serum samples examined, seven were found to contain only type 1 antibodies, 11 had type 2 antibodies alone, and six serum samples had both type 1 and type 2 antibodies. It is believed that a majority of the 17 patients whose acute serum samples already contained type 2 antibody were experiencing their first clinically apparent recurrence of a previous asymptomatic type 2 infection. Physicians should, therefore, acknowledge that patients with first-episode nonprimary herpes 2 infection may not have had a recent sexual contact with a herpes simplex virus-infected partner.