Under the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR), membrane filtration is designated as one of the "toolbox technologies" that may be used to achieve Cryptosporidium reduction. As a result, the Membrane Filtration Guidance Manual (MFGM) is being developed to assist the water treatment community with the implementation of membrane filtration for rule compliance. Because the MFGM describes the use of this rapidly expanding technology under the first federal level (i.e., nationwide) regulatory framework, the document has generated significant interest in the water treatment industry. However, it has become apparent that there is a significant gap in understanding between individuals who have examined the MFGM carefully and those who have reviewed it only superficially, even among professionals working within the membrane niche of the water industry. Although the regulatory framework for membranes developed under the LT2ESWTR is only specifically applicable to the reduction of Cryptosporidium in compliance with the rule, it is anticipated that primacy agencies may voluntarily adopt this framework in a broader context at the state level. As a result, the purpose of this paper is to dispel potential misconceptions about this regulatory framework and clarify important technical concepts as broadly and expediently as possible. The critical concepts addressed in the subsequent sections of this paper include the following: scope and purpose of the membrane regulatory framework; challenge testing vs. direct integrity testing; resolution vs. sensitivity; direct integrity testing vs. indirect integrity monitoring; control limits for integrity testing and monitoring; and, application and determination of the volumetric concentration factor.