The aim of this study was to investigate the relationship between adrenocortical function and chronic lung disease (CLD) of pre-term infants. Plasma F and ACTH were measured at 7, 14, 21 and 28 days of life in 25 pre-term infants with gestational age < or = 32 weeks and birth weight < or = 1,250 g. Fourteen infants developed CLD (CLD group) and 11 recovered without CLD (NOCLD group). Response to ACTH stimulation was tested on days 7 and 28. The results show that at the 7th day of life plasma F and ACTH levels were similar in the NOCLD and CLD group. CLD group had significantly higher plasma F and ACTH concentrations at the 14th (p=0.006 for F and p=0.020 for ACTH) and at the 21st (p=0.008 for F and p=0.024 for ACTH) day of life, while no significant differences were detected at the 28th day of life. The response to ACTH stimulation test was similar between the NOCLD and CLD group. These data demonstrate the lack of any significant association between adrenal insufficiency and CLD and discourage the use of baseline or stimulated plasma F levels to predict the development of CLD in pre-term infants.