Maintenance and repair processes are crucial to the pathogenesis of ageing and late-onset disease. Thus, there is increasing recognition of the importance of genetic factors in the development of late-onset conditions such as stroke, Parkinson's disease and osteoporosis, and accumulating evidence for a genetic component in the development of chronic obstructive pulmonary disease. We review the approaches and problems in the genetic investigation of complex disorders in old age, taking chronic obstructive pulmonary disease as an example.