To explore the value of antiandrogen therapy for advanced prostate cancer, two clinical trials of similar design were recently conducted in six countries throughout Europe. A total of 550 patients with previously untreated metastatic prostate cancer were randomized either to treatment with an antiandrogen or castration. While time to treatment failure, objective tumour response and survival were expected to be similar between study treatments, their effects on health-related quality of life (HRQOL) were expected to differ and were therefore a focus of concern in this trial. To assess these effects, we developed a brief self-administered patient questionnaire covering 10 domains of HRQOL (general health perceptions, pain, emotional well-being, vitality, social functioning, physical capacity, sexual interest, sexual functioning, activity limitation and bed disability), which we translated from English into several other languages. In this paper, we describe the development, content and translation of this survey instrument and report on its reliability and validity in six countries based on data collected for the first 487 patients to complete questionnaires at study entry.