A geographic cohort of babies born at less than 28 weeks in 1991-1992 in Australia was assessed at age 18. Brain volume was calculated using T1 weighted magnetic resonance imaging. Around one-third of these infants had received postnatal dexamethasone for bronchopulmonary dysplasia, with a cumulative mean dose of 7.7 mg/kg. These infants had smaller brain tissue volumes, for the brain overall, as well as for white matter, thalami and basal ganglia. There was a trend for higher doses of dexamethasone to be correlated with smaller brain (total and white matter) volumes.