Since 1989, the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) has been successful in implementing and completing health-related quality-of-life (HQL) assessments as part of phase III clinical trials. Compliance rates for completing HQL instruments remain high, with a minimal amount of missing data. It is believed that this success is attributable not only to the high degree of commitment to measuring HQL by clinical trials investigators, nurses, data managers, and central office administrative staff, but also to the educational process that was instituted after the development of a CTG policy for measuring HQL. From inception to May 1995, a total of 27 clinical trials with HQL assessment have been initiated or completed. In the majority of trials, the core HQL instrument is the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30). In addition to answering specific questions about HQL in these clinical trials, the trials provide the opportunity to do research into the measurement of HQL. Thus, current clinical trials include research questions about the appropriate timing of assessments, the reliability and validity of the QLQ-C30 and other instruments, the role of HQL data in assessing toxicity, and the significance of the results of HQL assessments. It is anticipated that this activity not only will be a rich source of information about the effects of cancer and its treatment on HQL but also will lead to improvements in measuring HQL in oncology.