Previous studies have provided conflicting evidence as to the possible benefits of inhaled corticosteroids in the treatment of chronic obstructive pulmonary disease (COPD). Using the Saskatchewan healthcare databases subjects were identified who were aged > or = 55 yrs, initiating regular treatment for COPD but without any prior treatment for asthma. In the current nested case-control analysis, the authors concentrated on 1,742 subjects with a first hospitalisation for COPD after January 1, 1990 and examined whether the use of inhaled corticosteroids was associated with a change in the risk of a subsequent hospitalisation for COPD. The cases consisted of 846 patients with a subsequent hospitalisation for COPD. These were matched on age, time since the prior hospitalisation and use of other respiratory therapy to all possible person moments in the cohort without rehospitalisation. After further adjustment for comorbidity, sex, calendar year and intensity of other drug therapy, inhaled corticosteroids were not significantly associated with risk of a subsequent COPD hospitalisation. Even relatively high doses of inhaled corticosteroids, >800 microg of beclomethasone or the equivalent per day, were not associated with the risk of COPD hospitalisation. No reduction in chronic obstructive pulmonary disease exacerbations requiring hospitalisation, in relation to the use of inhaled corticosteroids, were observed.