One of the complications of steroid therapy is the hypothalamic-pituitary-adrenal (HPA) axis' suppression, particularly in children where this can lead to growth suppression and other well known complications. Although there are a large number of studies on suppression of the HPA axis with the use of topical steroids, the subject is still controversial. We measured the HPA axis function in 3 groups of allergic children treated with: 1) intranasal beclomethasone dipropionate (BDP) 400 micrograms/day for 4 weeks or 2) BDP 800 micrograms/day for 4 weeks and 3) oral prednisone, 1 mg/kg/day for 2 weeks. The HPA response was obtained after lysine-vasopressin (LVP) stimulation. LVP acts on the pituitary or hypothalamus level, stimulating the whole axis. Peripheral blood samples through an intravenous line were obtained for serum cortisol measurement at zero, 30, 60, and 90 minutes after the intravenous injection of LVP, before and after the treatment period. Our results showed no suppression of the HPA axis in children medicated with BDP at either 400 micrograms/day or 800 micrograms/day. On the other hand, there was a suppression of the HPA axis after prednisone treatment (p < 0.05). During the LVP test some side effects, possibly due to systemic vasoconstriction, were noted such as abdominal pain, nausea and vomiting, and transient hypertension. In conclusion, intranasal BDP at the dose of 400 or 800 micrograms/day during 4 weeks did not induce HPA axis suppression. The LVP test is efficient to demonstrate HPA hypofunction or suppression and it produced only mild to moderate transient side effects. However, due to the side effects observed, a safer test such as urinary free cortisol (24 hours), should be used in the investigation of the HPA axis.