The field of health status and quality of life (QoL) measurement has evolved over the past 30 years, characterized by the proliferation of instruments with varying methods, content, and quality. The Medical Outcomes Trust (MOT) established a Scientific Advisory Committee (SAC) in 1994 to identify and review health status and QoL instruments for potential inclusion in a library for dissemination. The SAC defined a set of attributes and criteria for instrument assessments, which were updated in 1999 to reflect advancements in theories and technologies. These attributes include conceptual and measurement models, reliability, validity, responsiveness, interpretability, respondent and administrative burden, alternate forms, and cultural and language adaptations. The criteria provide guidelines for evaluating these attributes, aiming to promote the development and validation of high-quality instruments. The SAC's approach is applicable to both English-language and culturally adapted instruments, measuring health status and QoL in groups and individuals.The field of health status and quality of life (QoL) measurement has evolved over the past 30 years, characterized by the proliferation of instruments with varying methods, content, and quality. The Medical Outcomes Trust (MOT) established a Scientific Advisory Committee (SAC) in 1994 to identify and review health status and QoL instruments for potential inclusion in a library for dissemination. The SAC defined a set of attributes and criteria for instrument assessments, which were updated in 1999 to reflect advancements in theories and technologies. These attributes include conceptual and measurement models, reliability, validity, responsiveness, interpretability, respondent and administrative burden, alternate forms, and cultural and language adaptations. The criteria provide guidelines for evaluating these attributes, aiming to promote the development and validation of high-quality instruments. The SAC's approach is applicable to both English-language and culturally adapted instruments, measuring health status and QoL in groups and individuals.