This International Standard gives guidelines for monitoring and assessing the overall performance of a quantitative descriptive panel and the performance of each member. A panel of assessors can be used as an instrument to identify products’ sensory attributes and to assess the magnitude of sensory attributes. Performance is the measure of the ability of a panel or an assessor to make reliable and valid attribute assessments across the products being evaluated. It can be monitored at a given time point or tracked over time. Performance comprises the ability of a panel to detect, identify, and measure an attribute, use attributes in a similar way to other panels or between assessors within a panel, discriminate between stimuli, use a scale properly, repeat their own results, and reproduce results in comparison to other panels or assessors. The methods specified allow to monitor and assess the consistency, repeatability, freedom from bias and the ability of discrimination of panels and assessors. Monitoring and assessment can be carried out in one session or over time. Monitoring performance data enables the panel leader to improve panel and assessor performance, to identify issues and retraining needs or to identify assessors who are not performing well enough to continue participating. The methods specified in this International Standard can be used, in full or a selection only, by the panel leader to appraise continuously the performance of panels or individual assessors. The methods listed are not exhaustive and other appropriate methods may also be used. This International Standard applies to individuals or panels in training as well as for established panels.