This thesis consists of a collection of papers which are all concerned with mortality. Mortality is one of the most tangible expressions of that intangible "public health": the frequency and distribution of health problems in a population. The age at which people die, the conditions they die from, and many other aspects of mortality patterns provide important information on the occurrence of health problems in populations. The description and analysis of mortality patterns is therefore of interest to the health sciences, because differences in mortality between "times, places and persons" may suggest factors that play a causal role in the incidence or prognosis of specific health problems. The study of mortality may have a straightforward practical interest too, when it leads to the identification of health problems, geographical areas, population subgroups etc., where some kind of intervention is warranted. This may be an intervention through the health care system or through another agency, and will frequently have to be initiated by health policy makers. There are four interrelated themes in this thesis: Theme no. 1: The valid