The chemical diversity of natural antioxidants (AOXs) makes it difficult to separate, detect, and quantify individual antioxidants from a complex food/biological matrix. Moreover, the total antioxidant power is often more meaningful to evaluate health beneficial effects because of the cooperative action of individual antioxidant species. Currently, there is no single antioxidant assay for food labeling because of the lack of standard quantification methods. Antioxidant assays may be broadly classified as the electron transfer (ET)- and hydrogen atom transfer (HAT)-based assays. The results obtained are hardly comparable because of the different mechanisms, redox potentials, pH and solvent dependencies, etc. of various assays. This project will aid the identification and quantification of properties and mutual effects of antioxidants, bring a more rational basis to the classification of antioxidant assays with their constraints and challenges, and make the results more comparable and understandable. In this regard, the task group members convey their own experiences in various methods of antioxidants measurement.