A randomized study was designed to evaluate the effects of two different dexamethasone courses on the growth of preterm infants. The first phase included 30 preterm infants at high risk for chronic lung disease (CLD). 15 babies (moderately early dexamethasone group) were treated with dexamethasone for 14 days, from the 10th day of life, and received a total dose of 4.75 mg/kg; 15 babies were assigned to the control group. The second phase included 30 preterm infants at high risk for CLD. 15 babies (early dexamethasone group) were treated with dexamethasone for 7 days, from the 4th day of life, and received a total dose of 2.38 mg/kg; 15 babies were assigned to the control group. All the main clinical baseline characteristics were similar between the groups both in the first and in the second phase. Infants given the two dexamethasone courses showed significantly reduced weight gain during the period of treatment when compared to the respective control group, but they had a weight catch-up soon after the end of treatment. At 30 days of life the weight and length gain of each treated group were similar to those of control infants, but the moderately early dexamethasone group showed a significantly poorer head growth. No differences between the groups were observed at discharge. Dexamethasone treatment induces a slower weight gain which is time-limited to the period of treatment and is followed by a body weight catch-up. However, the poorer head growth detected at 30 days of life in the infants who received a higher dose of dexamethasone could indicate important adverse effects, possibly dose-related, on postnatal brain growth and development.