Summary: When examined by an egg-neutralization technique which employed preliminary incubation of virus-serum mixtures (1 hour at 37 C) human sera failed to exhibit “all or none” character of herpes antibody levels. The antibody titers of sera from herpetic individuals extended over more than a one thousandfold range. Significant fluctuation in herpes antibody titer was demonstrated in sera obtained from such individuals at different times.