We compared the clinical presentation of 95 newborns with herpes simplex virus (HSV) infection from 1973 through 1981 (first period) with data from 196 newborns evaluated from 1982 through 1987 (second period). There was a significant change in the presentation of infection in these infants. From the first to the second period, the frequency of disseminated disease decreased from 50.5% to 22.9%, whereas the frequency of skin, eye, and mouth (SEM) diseases increased from 17.9% to 43.4% (P less than .001). The frequency of infants with central nervous system (CNS) disease remained relatively unchanged--31.6% versus 33.7%. We also compared the demographic and clinical characteristics of the infants and their mothers. For neonates with CNS or disseminated infection, disease duration and frequency of prematurity were significantly decreased in the second period, as was the frequency of skin vesicles for newborns with SEM or disseminated infection. These changes are most likely the consequence of recognizing and treating SEM infection before its progression to more-severe disease.