Quality of life (QL) scores may be used to assess the impact of disease and treatment, and to predict survival of cancer patients in prospective clinical trials. The aim of this study was to evaluate the prognostic association of QL scores among patients with advanced malignancies in routine practice. Adult patients with advanced malignancy from 12 institutions in 10 countries completed the EORTC QLQ-C30 questionnaire, in their native language, once at study entry. Baseline patient and disease characteristics were recorded. We used a proportional hazards model stratified on diagnostic category to test whether QL scores from the QLQ-C30 were significantly and independently predictive of overall survival duration from the time of QL measurement. In all, 735 eligible patients were entered between November 1989 and September 1995. On 1 October 1995, follow-up information was obtained on 656 patients, of whom 411 had died. Patient and disease factors predictive of worse survival were age and performance status. The global scale and the scales of physical, role, emotional, cognitive and social function were each significantly predictive of subsequent survival duration in univariate analyses. Single-item QL scores for overall physical condition (question 29), overall quality of life (question 30), and the global and social functioning scales remained independently prognostic after allowing for performance status and age, and, among solid tumour patients, metastatic site. QL can be measured in an international setting based on routine oncology practice. QL scores carry prognostic information independent of other recorded factors.