In two mid-trimester fetuses with microcephaly, transvaginal sonography revealed aberrant findings, including large subarachnoid spaces and a rudimentary shape of the lateral ventricles. In one of these fetuses, power Doppler ultrasound demonstrated a discrepancy in the size of the signals generated by the intracranial arteries branching from the internal carotids and those branching from the vertebral arteries, and this was interpreted as the consequence of a reduced blood supply to the undersized cerebral hemispheres. We suggest that evaluation of intracranial anatomy by transvaginal sonography and power Doppler examination of the cerebral vessels may be of value in the diagnosis of fetal microcephaly.