ENThe purpose of this article is to demonstrate that historical demography, although not usually seen as a classic auxiliary science of history, can prove to be very helpful in research conducted by ‘traditional’ historians dealing with social, political or cultural history. This is shown with the help of selected examples concerning the life expectancy of members of historical populations, the age of marriage and the duration of marriage, the size of households, and the prevalence of migration. The data presented, primarily representing historical Poland and Lithuania, will indicate the benefits of incorporating demographic knowledge into standard historical analyses. Key words: historical demography, life expectancy, marriage, household, mobility.