The objective of this study was to obtain age- and sex-specific reference values for the European Organization for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire QLQ-C30. A randomly selected sample of the German adult population (3015 subjects) was used, 2081 subjects agreed to take part in the investigation. Most of the scales and symptom items of the questionnaire proved to be dependent on age and sex. Men reported fewer symptoms than women. Age differences were even more pronounced. Younger people reported better functioning and fewer symptoms. Compared with the results of a similar Norwegian study (Hjermstad MJ, Fayers PM, Bjordal K, Kaasa S. Health related quality of life in the general Norwegian population assessed by the European Organization for research and treatment of cancer core quality-of-life questionnaire: The QLQ-C30(+3). J Clin Oncol 1998, 16, 1188-1196) the prevalence of some symptoms was markedly less. Norm values for age and sex groups are given and regression analyses are performed which help to calculate expected mean scores. The results show that age and sex differences must be taken into consideration when different groups of cancer patients are compared. The norm values help to interpret quality of life data for clinicians.