This article applies the results of semi-structured qualitative interviews and twelve Clean Development Mechanism (CDM) case studies to determine whether the designation of a materiality threshold at the UNFCCC CDM Executive Board level would, with respect to proposed Brazilian CDM projects, be likely to achieve such materiality standard’s stated objectives of (a) streamlined CDM procedures that reduce transactions costs, (b) enhanced objectivity of variable designated operational entity (DOE) judgments, and (c) enhanced consistency. It finds that Brazil’s overriding objective is to ensure that greenhouse gas emission reductions comprise real reductions encompassing appropriate (i.e., conservative) project methodologies, baselines and additionality in a manner that strictly preserves the CDM’s inherent environmental integrity as an offset mechanism which may have the potential to impede some cost reductions arising from streamlined CDM procedures and other procedural efficiencies sought by proponents of a CDM materiality standard.