Quality of life (QOL) assessment may improve the evaluation of treatment for oesophageal cancer but patient compliance using self completion questionnaires is often poor. The use of a proxy to estimate QOL might improve data collection from patients who are either unable or unwilling to complete the questionnaire. This study examined whether a doctor or patients' carers could accurately assess QOL using the QLQ-C30 questionnaire developed by the European Organisation for Research and Treatment of Cancer Study Group on Quality of Life. One doctor, 52 patients and 39 carers completed the instrument independently. Proxy and patient ratings were analysed for agreement using weighted kappa scores. Agreement was poor or moderate in most QOL scales and items (kappa < or = 60). This study demonstrates that a carer or doctor is not sufficiently accurate to postulate the patient's responses to the questionnaire. Quality of life data, therefore, should come from the patients themselves.