Supposedly some people take the HTS first becasue you can cough out a lot of the Pulmozyme if you do it the other ways around. I actually take Pulmozyme first because of the time issue as well as the fact that I feel it works better. My doctor said it really has no basis doing it either way- so I should just do what makes me do it the most or what I feel is most effective. I cough out a lot of mucus if I do the Pulmozyme first (I wait a while in between if possible so it can get working). I feel that I clear out more, and my FEV1 has gone up so it works for me, but maybe not for people who are more time constrained or cough up alot of mucus.