For phage therapy to advance to more systematic applications, it is generally accepted that data demonstrating safety and effectiveness, derived from controlled clinical studies, will be required. Such trials are underway (see clinical.trials.gov) under the auspices of the FDA, in the US. In addition to these controlled trials, phage preparations are being used under the FDA’s expanded access provisions (often referred to as compassionate use). FDA has been reviewing such submissions for many years now and has found that, although phage therapy presents unique challenges in some ways, existing regulatory pathways, informed by the available scientific data on phage and phage therapy, have been sufficient to these tasks, and have allowed phage therapy studies to progress. In FDA’s review of phage therapy submissions, Chemistry, Manufacturing, and Control (CMC) information is crucial. This talk will present i) the agency’s current expectations regarding the CMC information that is necessary to provide assurances that a phage product used in humans will be safe and will stand the best chances of being effective; and ii) how this information is expected to develop as a product moves through the stages of clinical development. Topics such as desirable characteristics of phage used for treatment, host strain selection, methods of purification, identification of, and control of, impurities, and stability assessment will be discussed.