Although it is believed, in theory, that inhaled steroids should be useful for most CF patients, we are not sure how well they work in CF and it has not yet been possible to prove this with standard studies. This would normally involve starting inhaled steroids in patients who have not been taking them. We have therefore taken a different approach, namely to withdraw them from some patients who have been on them for a long time, to see if there is any effect of stopping them.