The field of health status and quality of life (QoL) measurement has evolved over the past 30 years, developing into a formal discipline with a theoretical framework, accepted methods, and diverse applications. In 1994, the Medical Outcomes Trust (MOT) established a Scientific Advisory Committee (SAC) to evaluate health status and QoL instruments and create an instrument library for dissemination. The SAC defined key attributes and review criteria for instrument assessments in the mid-1990s, which were updated five years later to reflect new theories and technologies. This paper outlines the SAC's current conceptualization of eight key attributes of health status and QoL instruments: conceptual and measurement model, reliability, validity, responsiveness, interpretability, respondent and administrative burden, alternate forms, and cultural and language adaptations. The paper also presents the criteria by which instruments would be reviewed on each of these attributes. These guidelines are suggested for the field to consider and debate, with the expectation that experts will update and refine them as measurement techniques become more sophisticated. The SAC's approach includes defining instruments as the set of items in questionnaires and interview schedules along with their instructions, procedures, and other materials. The criteria are used to evaluate instruments developed in English and their cultural and language adaptations, but they can also be applied to instruments developed in other languages. The criteria apply to instruments that measure domains of health status and QoL in both groups and individuals. The SAC's work aims to ensure that instruments are reliable, valid, and responsive to changes in health status and QoL, while also considering the burden on respondents and administrators, as well as cultural and language adaptations. The SAC's guidelines are intended to help the field of health status and QoL measurement improve the quality and consistency of instruments used in research and practice.The field of health status and quality of life (QoL) measurement has evolved over the past 30 years, developing into a formal discipline with a theoretical framework, accepted methods, and diverse applications. In 1994, the Medical Outcomes Trust (MOT) established a Scientific Advisory Committee (SAC) to evaluate health status and QoL instruments and create an instrument library for dissemination. The SAC defined key attributes and review criteria for instrument assessments in the mid-1990s, which were updated five years later to reflect new theories and technologies. This paper outlines the SAC's current conceptualization of eight key attributes of health status and QoL instruments: conceptual and measurement model, reliability, validity, responsiveness, interpretability, respondent and administrative burden, alternate forms, and cultural and language adaptations. The paper also presents the criteria by which instruments would be reviewed on each of these attributes. These guidelines are suggested for the field to consider and debate, with the expectation that experts will update and refine them as measurement techniques become more sophisticated. The SAC's approach includes defining instruments as the set of items in questionnaires and interview schedules along with their instructions, procedures, and other materials. The criteria are used to evaluate instruments developed in English and their cultural and language adaptations, but they can also be applied to instruments developed in other languages. The criteria apply to instruments that measure domains of health status and QoL in both groups and individuals. The SAC's work aims to ensure that instruments are reliable, valid, and responsive to changes in health status and QoL, while also considering the burden on respondents and administrators, as well as cultural and language adaptations. The SAC's guidelines are intended to help the field of health status and QoL measurement improve the quality and consistency of instruments used in research and practice.