In two studies comparing budesonide delivered by Turbuhaler with budesonide delivered by pressurized metered dose inhaler (pMDI), a significantly higher morning peak expiratory flow (PEF), and a patient preference in favor of budesonide by Turbuhaler was found. Less cough was also noted. In a third study no difference was found between the two formulations. However, a meta-analysis of the three studies demonstrated a significant difference in favor of budesonide by Turbuhaler for forced expiratory volume in one second (FEV1) and morning PEF. These findings are supported by data on lung deposition showing the Turbuhaler to be twice as efficient as a pMDI. At the same time, the availability of budesonide from the gastrointestinal tract is reduced. Thus, a more beneficial ratio arises between local lung delivery and systemic availability. Inhaled glucocorticosteroids are now recommended for mild asthma. Thus once daily treatment with 400mug budesonide by Turbuhaler has been studied in two trials; a comparison with 200mug twice daily was also made. In both studies morning/evening PEF increased significantly over placebo and no difference was demonstrated between once- and twice-daily treatments. A study to determine the effect of placebo and 200mug twice daily and 400mug once daily of budesonide by Turbuhaler on 24-h plasma and urinary cortisol demonstrated no difference between the treatment regimens. Budesonide by Turbuhaler is at least as effective as budesonide by pMDI. When patients are switched to budesonide by Turbuhaler an attempt should be made to reduce the dose.(ABSTRACT TRUNCATED AT 250 WORDS)