Despite growing acceptance that patients have the clearest view of the health outcomes that matter, drugs to treat rare diseases often live or die on outcome measures that may fail to reflect their benefits to patients. As a result, regulatory approval and reimbursement decisions may made in the absence of measures of meaningful health outcomes for patients. We spoke to Thomas Morel, a research fellow at KU Leuven in Belgium and co-author of an article in the November issue of the Orphanet Journal of Rare Diseases, about the particular challenges of rare disease clinical trials, the importance of patient-centered outcome measures for them, and what it will take to develop and use such measures for rare disease clinical studies.