Epidemiological studies have indicated an association between influenza A virus infections during fetal life and neuropsychiatric diseases. To study the potential for influenza A virus infections to cause nervous system dysfunctions, we describe a mouse model using intranasal instillation of the mouse neuroadapted influenza A/WSN/33 strain in pregnant mice. Viral RNA and nucleoprotein were detected in fetal brains and the viral RNA persisted for at least 90 days of postnatal life. We have, thus, obtained evidence for transplacental passage of influenza virus in mice and the persistence of viral components in the brains of these animals into young adulthood.