We report a case of eradication of Viridans streptococci from the amniotic cavity in a patient with preterm labor and intact membranes by transplacental antibiotic treatment. Following this modality of treatment, preterm labor was arrested and the pregnancy continued uneventfully until normal term delivery. We suggest that transplacental antibiotic treatment should be seriously considered as part of the medical armamentarium for treatment of patients with preterm labor and microbial invasion of the amniotic cavity.