FDA has released a draft guidance document addressing the interpretability of non-inferiority (NI) clinical trials, as well as the proper approaches for determining the NI margin and analyzing results. The draft guidance contains four sections, which discuss: (1) the regulatory, study design, scientific, and statistical issues associated with NI studies for the purpose of showing efficacy; (2) the quantitative analytical and statistical approaches used to determine the NI margin for use in NI studies; (3) commonly asked questions about NI studies and provides practical advice about various approaches; and (4) five examples of successful and unsuccessful efforts to define NI margins and conduct NI studies. FDA is accepting comments on the draft guidance until June 1, 2010.