Virus isolation tests were performed during the first, second, and third trimesters of pregnancy on a group of 163 students who received prenatal care at the University of Chile's Student Medical and Dental Service to determine the possible existence of genital herpes or cytomegalovirus infections. Vaginal secretion samples tested for herpes simplex virus (HSV) and urine samples tested for cytomegalovirus (CMV) were inoculated onto cell cultures and examined by immunofluorescent procedures using monoclonal antibodies. HSV was detected in five subjects, only one of whom had herpetic lesions, and was identified as type 2 in all cases. Cytomegalovirus was detected in seven subjects.