Background: BPD is generally observed in premature neonates needing oxygen (direct or ventilated), and to reduce its effects various studies have been carried out with different results. In this study the effect of vitamin A in prevention of chronic lung disease in premature neonates under 2500 gr was investigated in Zanjan within the years 2003-2004. Materials and Methods: In this double blind clinical trial premature neonates under 36 weeks of age and birth weight of under 2500 gr were included in the study in case of need to oxygen during first three days of birth and neonates who died during three days of birth and those with congenital disorders and distinct heart condition were excluded from the study. At first 66 neonate were selected of whom 12 cases were excluded from the study. The survivors were randomly categorized into two groups: a control (28 cases) and a treatment (26 cases). Treatment group received 10000 IU vitamin A intramuscularly on the 4th and the 8th days. The variables need to complementary oxygen – neonate weight on 28th day, and mortality rate up to 28th day – were considered as outcome indices. The results were analyzed through statistical tests , relative risk and 95% confidence interval in community. Results: 54 neonates were followed up to 28 days following birth. One case from treatment group and 3 cases from control group died before reaching the 28th day. Of 50 survivors 6 cases in treatment and 12 cases in control group were found to be oxygen dependent (Oxygen Saturation <95%). On the 28th day no significant difference was observed between the two groups in weight gain (p=96%) need to oxygen (p=77%) and mortality rate (p=336%). Conclusion: Although the results of this study show no decline in BPD rate, mortality rate and no gain in weight of neonates, we can not reject the effect of vitamin A with higher doses. Thus, further research with higher sample size and higher dose of vitamin A specially in neonates under 1500 gr of weight is recommended.