The Malmö Diet and Cancer study is a 10-year prospective case-control study in 45-64-year-old men and women (n = 53,000) living in a city with 230,000 inhabitants. One objective is to clarify whether a western diet is associated with certain forms of cancer whilst taking other life-style factors into account. Another broad question is whether oxidative stress and the activity in DNA-repairing systems influence the impact of diet on the development of all or certain forms of cancer. The study is also to act as a resource available for testing new hypotheses emanating from other studies. Initially food intake, heredity, socio-economic factors, life-style pattern, occupational situation, previous and current diseases, symptoms and medications, will be determined. Viable lymphocytes, granulocytes, erythrocytes, and plasma/serum will be stored in a biological bank together with tumour specimens gathered from cases. The incidence and mortality of all cancer forms will then be followed for 10 years by existing registries. Data from the initial examination in these cases will then be compared with those of control subjects not having developed any form of cancer. A biomarker programme, utilizing the biological bank, has been developed and is aimed at finding predictors and/or precursors of cancer. A high participation rate (> 70%) and a high quality biological bank are prerequisites for a successful project. The experience gathered so far indicates that these goals are feasible.