The Health Utilities Index (HUI®) is a comprehensive, preference-based system for measuring health status and health-related quality of life (HRQL). It consists of two main components: HUI Mark 2 (HUI2) and HUI Mark 3 (HUI3), which together describe nearly 1,000,000 unique health states. HUI provides single- and multi-attribute utility scoring systems that are reliable, valid, and responsive. The classification systems link directly with preference-based scoring models, converting descriptive information into utility scores. HUI questionnaires are available in multiple languages and formats, including self-completion and interviewer-administered versions, and can be used in both clinical and general population studies. HUI has been widely used in clinical studies and large-scale population surveys, providing valuable data for interpreting results and comparing disease and treatment outcomes. Future developments include a web-based system for real-time data collection and analysis.The Health Utilities Index (HUI®) is a comprehensive, preference-based system for measuring health status and health-related quality of life (HRQL). It consists of two main components: HUI Mark 2 (HUI2) and HUI Mark 3 (HUI3), which together describe nearly 1,000,000 unique health states. HUI provides single- and multi-attribute utility scoring systems that are reliable, valid, and responsive. The classification systems link directly with preference-based scoring models, converting descriptive information into utility scores. HUI questionnaires are available in multiple languages and formats, including self-completion and interviewer-administered versions, and can be used in both clinical and general population studies. HUI has been widely used in clinical studies and large-scale population surveys, providing valuable data for interpreting results and comparing disease and treatment outcomes. Future developments include a web-based system for real-time data collection and analysis.