Forty children aged 1-3 y completed a placebo-controlled study on the effects of 10 d of inhaled budesonide for asthma caused by respiratory tract infection. The effects on symptoms were significantly better in the active than in the placebo group. In 20 of these children the systemic effects of high-dose inhaled budesonide for 10 d and the effect of a 3-d course of oral betamethasone on asthma exacerbation were evaluated. Systemic effects were evaluated by measuring morning cortisol in serum and urine, and the bone markers osteocalcin, ICTP (the C-terminal telopeptide region of type I collagen) and PIIINP (an N-terminal propeptide of type III procollagen) in serum before and at the end (d 7-10) of treatment (1600 microg budesonide d(-1) for 3 d and 800 microg for 7 d). In 9 children, measurements were taken on d 3 of a 3-d course of betamethasone (6, 4 and 2 mg) for asthma exacerbation and 14 d later. There were no signs of systemic effects after 7-10 d of budesonide. After 3 d of betamethasone, serum cortisol decreased from a median of 263 to 26 nmol l(-1), urine cortisol/creatinine from 19.9 to 7.2 nmol l(-1), osteocalcin from 31.4 to 5.5 microg l(-1), ICTP from 19.4 to 8.5 microg l(-1) and PIIINP from 12.3 to 5.9 microg l(-1). Two weeks later, the levels were back to normal. In conclusion, short courses of oral betamethasone have pronounced systemic effects, whereas 10 d of high doses of budesonide do not produce significant systemic effects.