Disseminated herpes simplex virus infection during pregnancy is uncommon but is accompanied by high maternal and fetal morbidity and mortality. Pregnant women with primary mucous membrane infection during the third trimester may run an increased risk for dissemination, although specific predisposing factors are unknown. Diagnosis requires awareness of the clinical syndrome, a high index of suspicion in the proper setting, and appropriate use of available diagnostic techniques. Although the disease may be self-limited, mortality approaches 40% for mother and fetus. In the presence of severe or progressive systemic infection, specific antiviral chemotherapy with vidarabine may be warranted. Management of the fetus remains problematic; prompt delivery by cesarean section may be indicated.