Molecular epidemiology is a discipline in which the methods of molecular biology are applied to human populations. We have developed a battery of methods for measuring diverse kinds of DNA damage, and capacities for DNA repair, in human lymphocytes. These biomarkers allow us to investigate the impact of environmental factors, lifestyle, nutrition, sex and genetic polymorphisms on genomic instability, which is assumed to be causally related to aging and cancer. First, we need to establish mean baseline val ues for the various biomarkers, and the range found in a normal healthy population. To this end, we have collected and stored samples from about 300 subjects in the 'Norwegian Baseline Study'. These samples await analysis. The Yggdrasil scholar will learn the necessary techniques, carry out certain method development (to optimise the DNA repair assays), and then analyse as many stored samples as possible in the time available. The ultimate aim is two-fold: first, to investigate associations between the pa rameters we measure and the anthropometric and nutritional information gathered by colleagues involved in this study; and second, to contribute to the database being established under ComNet, a new project to validate the comet assay as a biomonitoring to ol, and to establish reference values of biomarkers for future comparisons.