A service-oriented screening program for serologic detection of viral and parasitic infections during gestation is described for three different population groups. Significance of a determination of primary cytomegalovirus infection is documented. A screening program for detection of immunity to rubella is recommended, but the feasibility of similar programs for herpes simplex virus and Epstein-Barr virus warrants further study. Because of the low frequency of toxoplasmosis, education of patients instead of screening may be appropriate.