Class-specific immune response in acute herpes simplex virus (HSV) infections to individual virus specified polypeptide antigens was analysed by immunoblotting. The HSV specified glycoproteins B (gB), C (gC), and D (gD) were detected. IgG-antibody response was shown to develop to various other virus specific polypeptides as well. The IgM- and IgA-antibody responses remained restricted to only a few HSV specific proteins, namely VP 13 (80 kD), VP 20 (52 kD), and VP 23 (40 kD) and to the low molecular weight polypeptides.