44 infants under 1 year were studied retrospectively during there acute illness and follow up after 1 week intervals. the spectrum of sonographic features of bacterial meningitis in acute stage included normal scan(20 patients). echogenic sulci (10 patients) echogenic linings of ependymas (8 patients) Abnormal parenchymal echogenecity (6 patients). On follow up examination with 1 week intervals a variety of complications was found in 14 patients.(32 %) of the infants. there were ventriculomegaly in 7 patients. extraaxial fluid collection in 4 patients brain abscess in 2 patients and poor encephalic cyst in 1 patient. We concluded that ultrasound was an effective menhod for evaluation of progression and complications of bacterial meningitis.