Reliable and defensible data quality underpins the value and validity of decisions made by dietary supplement manufacturers, consumers, and regulatory investigators. Over the past few years, the dietary supplement industry has been pummeled by the news media about the quality, reliability, and utility of the products it sells. Sometimes the charges are justified, but often the claims are biased, inaccurate, or misinterpreted, and often the data used by investigators are not validated or transparent. This paper will initially provide a primer into the elements of a quality assurance program that provide sound scientific data, then will review regulatory requirements for testing conducted by manufacturers, critique third-party investigations of OTC dietary supplement products, and, finally, provide suggestions to investigators about how to structure a testing program that will produce defensible results, that should, if needed, be admissible in court.