Fecal microbiota transplantation (FMT) is an effective treatment for Clostridium difficile infections that are refractory to antibiotic therapy. Because of the important roles of the microbiota in the function of the gastrointestinal tract and other aspects of human physiology, there is a growing interest in studying FMT for other clinical indications. The US Food and Drug Administration regulates clinical studies to evaluate the safety and efficacy of FMT. Studies of FMT for recurrent Clostridium difficile infection or other indications could require submission of an investigational new drug application. Most academic physicians and investigators do not have the regulatory experience necessary to undertake this process. We provide guidance to researchers on the preparation and submission of investigational new drug applications to study FMT.