STUDY SUMMARY This study will include about 40 subjects at National Jewish Health. This is a "double blind study" which means neither the subject nor the study staff will know if the subject is get pirfenidone or placebo during the study. This is done to be sure that no one knows who is getting pirfenidone or placebo and the effects of the treatment can be measured objectively, without bias. Subject's that enroll in this study will have an equal chance of getting pirfenidone or placebo. The decision about which treatment the subject will receive (randomization) is made through a central organization.