Research in our group is focused on elucidating the molecular mechanism of Nucleotide Excision Repair (see figure) and its impact on human health. Nucleotide Excision Repair (abbreviated as NER) is an important DNA repair mechanism able to remove a broad range of different DNA damages. NER protects organisms against DNA damage-induced carcinogenesis and premature ageing. Its significance is illustrated by the severe clinical consequences of inherited defects in NER. Genetic defects in NER give rise to a triad of syndromes, which include the cancer-prone and photo-hypersensitivity disease Xeroderma Pigmentosum (XP), the premature ageing Cockayne s Syndrome (CS) and the brittle hair disorder Trichothiodystrophy (TTD). We apply a multidisciplinary approach to improve our understanding of the molecular mechanism of NER, working at the molecular genetic, biochemical and cell biological level, to the level of intact mammalian organisms and patients.