Noninferiority (NI) trials in drug research are used for the purpose of demonstrating that a new treatment is not worse than a proven active comparator, thereby indirectly showing that the treatment is effective. This article explains and addresses the complications in the interpretation of NI trials that arise from the indirect comparison. On the basis of our review of 232 trials, we conclude that the interpretation and inference of NI trials are complicated, partly because of the incompleteness of the information.