Several studies have shown that growth hormone deficiency in adults leads to poor well-being and other clinical consequences, and that these improve when the hormone is replaced. However, the studies employed generic measures of health status that miss important aspects of the patients' experience and that have inadequate reliability and responsiveness. This paper describes the European development and testing of the Quality of Life-Assessment of Growth Hormone Deficiency in Adults (QoL-AGHDA), a condition-specific quality of life measure for use in clinical trials and for the routine monitoring of patients. The instrument was produced in five languages; English, Swedish, Italian, German and Spanish. Each language version is shown to have good reliability, internal consistency and construct validity. The QoL-AGHDA is currently included in an international database monitoring the long-term efficacy and safety of growth hormone replacement therapy and in clinical trials in a number of countries.